Low-Temperature Cross-Linked Hole Transport Layer for High-Performance Blue Quantum-Dot Light-Emitting Diodes

Quantum-dot light-emitting diodes (QLEDs), a kind of promising optoelectronic device, demonstrate potential superiority in next-generation display technology. Thermal cross-linked hole transport materials (HTMs) have been employed in solution-processed QLEDs due to their excellent thermal stability and solvent resistance, whereas the unbalanced charge injection and high cross-linking temperature of cross-linked HTMs can inhibit the efficiency of QLEDs and limit their application. Herein, a low-temperature cross-linked HTM of 4,4'-bis(3-(((4-vinylbenzyl)oxy)methyl)-9H-carbazol-9-yl)-1,1'-biphenyl (DV-CBP) with a flexible styrene side chain is introduced, which reduces the cross-linking temperature to 150 °C and enhances the hole mobility up to 1.01 × 10-3 cm2 V-1 s-1. More importantly, the maximum external quantum efficiency of 21.35% is successfully obtained on the basis of the DV-CBP as a cross-linked hole transport layer (HTL) for blue QLEDs. The low-temperature cross-linked high-mobility HTL using flexible side chains could be an excellent alternative for future HTL development.

Dynamic Reversible Oxidation-Reduction of Iodide Ions for Operationally Stable Perovskite Solar Cells under ISOS-L-3 Protocol

Despite rapid advancements in the photovoltaic efficiencies of perovskite solar cells (PSCs), their operational stability remains a significant challenge for commercialization. This instability mainly arises from light-induced halide ion migration and subsequent oxidation into iodine (I2). The situation is exacerbated when considering the heat effects at elevated temperatures, leading to the volatilization of I2 and resulting in irreversible device degradation. Mercaptoethylammonium iodide (ESAI) is thus incorporated into perovskite as an additive to inhibit the oxidation of iodide anion (I-) and  the light-induced degradation pathway of FAPbI3→FAI+PbI2. Additionally, the formation of a thiol-disulfide/I--I2 redox pair within the perovskite film provides a dynamic mechanism for the continuous reduction of I2 under light and thermal stresses, facilitating the healing of iodine-induced degradations. This approach significantly enhances the operational stability of PSCs. Under the ISOS-L-3 testing protocol (maximum power point (MPP) tracking in an environment with relative humidity of ≈50% at ≈65 °C), the treated PSCs maintain 97% of their original power conversion efficieney (PCE) after 300 h of aging. In contrast, control devices exhibit almost complete degradation, primarily due to rapid thermal-induced I2 volatilization. These results demonstrate a promising strategy to overcome critical stability challenges in PSCs, particularly in scenarios involving thermal effects.

New Nanophotonics Approaches for Enhancing the Efficiency and Stability of Perovskite Solar Cells

Over the past decade, the power conversion efficiency (PCE) of perovskite solar cells (PSCs) has experienced a remarkable ascent, soaring from 3.8% in 2009 to a remarkable record of 26.1% in 2023. Many recent approaches for improving PSC performance employ nanophotonic technologies, from light harvesting and thermal management to the manipulation of charge carrier dynamics. Plasmonic nanoparticles and arrayed dielectric nanostructures have been applied to tailor the light absorption, scattering, and conversion, as well as the heat dissipation within PSCs to improve their PCE and operational stability. In this review, it is begin with a concise introduction to define the realm of nanophotonics by focusing on the nanoscale interactions between light and surface plasmons or dielectric photonic structures. Prevailing strategies that utilize resonance-enhanced light-matter interactions for boosting the PCE and stability of PSCs from light trapping, carrier transportation, and thermal management perspectives are then elaborated, and the resultant practical applications, such as semitransparent photovoltaics, colored PSCs, and smart perovskite windows are discussed. Finally, the state-of-the-art nanophotonic paradigms in PSCs are reviewed, and the benefits of these approaches in improving the aesthetic effects and energy-saving character of PSC-integrated buildings are highlighted.

Enhancing Stability and Performance in Tin-Based Perovskite Field-Effect Transistors Through Hydrogen Bond Suppression of Organic Cation Migration

Ion migration poses a substantial challenge in perovskite transistors, exerting detrimental effects on hysteresis and operational stability. This study focuses on elucidating the influence of ion migration on the performance of tin-based perovskite field-effect transistors (FETs). It is revealed that the high background carrier density in FASnI3 FETs arises not only from the oxidation of Sn2+ but also from the migration of FA+ ions. The formation of hydrogen bonding between FA+ and F- ions efficiently inhibits ion migration, leading to a reduction in background carrier density and an improvement in the operational stability of the transistors. The strategy of hydrogen bond is extended to fluorine-substituted additives to improve device performance. The incorporation of 4-fluorophenethylammonium iodide additives into FETs significantly minimizes the shift of turn-on voltage during cyclic measurements. Notably, an effective mobility of up to 30 cm2 V-1 s-1 with an Ion/off ratio of 107 is achieved. These findings hold promising potential for advancing tin-based perovskite technology in the field of electronics.

Bright and Stable Red Perovskite LEDs under High Current Densities

Perovskite LEDs (PeLEDs) have emerged as a next-generation light-emitting technology. Recent breakthroughs were made in achieving highly stable near-infrared and green PeLEDs. However, the operational lifetimes (T50) of visible PeLEDs under high current densities (>10 mA cm-2) remain unsatisfactory (normally <100 h), limiting the possibilities in solid-state lighting and AR/VR applications. This problem becomes more pronounced for mixed-halide (e.g., red and blue) perovskite emitters in which critical challenges such as halide segregation and spectral instability are present. Here, we demonstrate bright and stable red PeLEDs based on mixed-halide perovskites, showing measured T50 lifetimes of up to ∼357 h at currents of ≥25 mA cm-2, a record for the operational stability of visible PeLEDs under high current densities. The devices produce intense and stable emission with a maximum luminance of 28,870 cd m-2 (radiance: 1584 W sr-1 m-2), which is record-high for red PeLEDs. Key to this demonstration is the introduction of sulfonamide, a dipolar molecular stabilizer that effectively interacts with the ionic species in the perovskite emitters. It suppresses halide segregation and migration into the charge-transport layers, resulting in enhanced stability and brightness of the mixed-halide PeLEDs. These results represent a substantial step toward bright and stable PeLEDs for emerging applications.

Interfacial Passivation Engineering for Highly Efficient Quantum Dot Light-Emitting Diodes via Aromatic Amine-Functionalized Dipole Molecules

Blue quantum dot (QD) light-emitting diodes (QLEDs) exhibit unsatisfactory operational stability and electroluminescence (EL) properties due to severe nonradiative recombination induced by large numbers of dangling bond defects and charge imbalance in QD. Herein, dipolar aromatic amine-functionalized molecules with different molecular polarities are employed to regulate charge transport and passivate interfacial defects between QD and the electron transfer layer (ETL). The results show that the stronger the molecular polarity, especially with the -CF3 groups possessing a strong electron-withdrawing capacity, the more effective the defect passivation of S and Zn dangling bonds at the QD surface. Moreover, the dipole interlayer can effectively reduce electron injection into QD at high current density, enhancing charge balance and mitigating Joule heat. Finally, blue QLEDs exhibit a peak external quantum efficiency (EQE) of 21.02% with an operational lifetime (T50 at 100 cd m-2) exceeding 4000 h.

B-N Covalent Bond Embedded Double Hetero-[n]helicenes for Pure Red Narrowband Circularly Polarized Electroluminescence with High Efficiency and Stability

Chiral B/N embedded multi-resonance (MR) emitters open a new paradigm of circularly polarized (CP) organic light-emitting diodes (OLEDs) owing to their unique narrowband spectra. However, pure-red CP-MR emitters and devices remain exclusive in literature. Herein, by introducing a B-N covalent bond to lower the electron-withdrawing ability of the para-positioned B-π-B motif, the first pair of pure-red double hetero-[n]helicenes (n = 6 and 7) CP-MR emitter peaking 617 nm with a small full-width at half-maximum of 38 nm and a high photoluminescence quantum yield of ≈100% in toluene is developed. The intense mirror-image CP light produced by the enantiomers is characterized by high photoluminescence dissymmetry factors (gPL ) of +1.40/-1.41 × 10-3 from their stable helicenes configuration. The corresponding devices using these enantiomers afford impressive CP electroluminescence dissymmetry factors (gEL ) of +1.91/-1.77 × 10-3 , maximum external quantum efficiencies of 36.6%/34.4% and Commission Internationale de I'Éclairage coordinates of (0.67, 0.33), exactly satisfying the red-color requirement specified by National Television Standards Committee (NTSC) standard. Notably a remarkable long LT95 (operational time to 95% of the initial luminance) of ≈400 h at an initial brightness of 10,000 cd m-2 is also observed for the same device, representing the most stable CP-OLED up to date.

Bilayer 2D-3D Perovskite Heterostructures for Efficient and Stable Solar Cells

With a stacking-layered architecture, the bilayer two-dimensional-three-dimensional (2D-3D) perovskite heterostructure (PHS) not only eliminates surface defects but also protects the 3D perovskite matrix from external stimuli. However, these bilayer 2D-3D PHSs suffer from impaired interfacial charge carrier transport due to the relatively insulating 2D perovskite fragments with a random phase distribution. Over the past decade, substantial efforts have been devoted to pioneering molecular and structural designs of the 2D perovskite interlayers for improving their charge carrier mobility, which enables state-of-the-art perovskite solar cells with high power conversion efficiency and exceptional operational stability. Herein, this review offers a comprehensive and up-to-date overview on the recent progress of bilayer 2D-3D PHSs, encompassing advancements on spacer cation engineering, interfacial charge carrier modification, advanced deposition protocols, and characterization techniques. Then, the evolutionary trajectory of bilayer 2D-3D PHSs is outlined by summarizing its mainstream development trends, followed by a perspective discussion about its future research opportunities toward efficient and durable perovskite solar cells.

Uracil Induced Simultaneously Strengthening Grain Boundaries and Interfaces Enables High-Performance Perovskite Solar Cells with Superior Operational Stability

The operational stability is a huge obstacle to further commercialization of perovskite solar cells. To address this critical issue, in this work, uracil is introduced as a "binder" into the perovskite film to simultaneously improve the power conversion efficiency (PCE) and operational stability. Uracil can efficiently passivate defects and strengthen grain boundaries to enhance the stability of perovskite films. Moreover, the uracil also strengthens the interface between the perovskite and the Tin oxide (SnO2 ) electron transport layer to increase the binding force. The uracil-modified devices deliver a champion PCE of 24.23% (certificated 23.19%) with negligible hysteresis at active area of 0.0625 cm2 . In particular, the optimal device exhibits over 90% of its initial PCE after tracking for ≈6000 h at its maximum power point under continuous light, indicating its superior operational stability. Moreover, the devices also show great reproducibility in both PCE and operational stability.

Highly efficient isolation and purification of high-purity tea saponins from industrial camellia oil production by porous polymeric adsorbents

BACKGROUND

Recovery of high-purity tea saponin (TS), a promising non-ionic surfactant with well-documented properties, is one of the major challenges to broadening its industrial applications. In this study, an innovative and sustainable strategy for the highly-efficient purification of TS was developed by using well-designed highly-porous polymeric adsorbents.

RESULTS

The prepared Pp-A with controllable macropores (~96 nm) and appropriate surface hydrophobic properties was found more favorable for achieving high adsorption efficiency towards TS/TS-micelles. Kinetic results showed the adsorption follows the pseudo-second-order model (R2  = 0.9800), and the Langmuir model is more qualified to explicate the adsorption isotherms with Qe-TS  ~ 675 mg g-1 . Thermodynamic studies revealed the monolayer adsorption of TS was an endothermic process that was conducted spontaneously. Interestingly, ethanol-driven desorption (90% v/v ethanol) of TS was rapidly (< 30 min) complete due to the possible ethanol-mediated disassembling of TS-micelles. A possible mechanism that involves the interactions between the adsorbents and TS/TS-micelles, the formation and disassembling of TS-micelles was proposed to account for the highly efficient purification of TS. Afterwards, Pp-A-based adsorption method was developed to purify TS directly from industrial camellia oil production. Through selective adsorption, pre-washing, and ethanol-driven desorption, the applied Pp-A enabled the direct isolation of high-purity TS (~96%) with a recovery ratio > 90%. Notably, Pp-A exhibited excellent operational stability and is of high potential for long-term industrial application.

CONCLUSION

Results ensured the practical feasibility of the prepared porous adsorbents in purifying TS, and the proposed methodology is a promising industrial-scale purification strategy. © 2023 Society of Chemical Industry.

Thermal Management Enables Stable Perovskite Nanocrystal Light-Emitting Diodes with Novel Hole Transport Material

The severely insufficient operational lifetime of perovskite light-emitting diodes (LEDs) is incompatible with the rapidly increasing external quantum efficiency, even as it approaches the theoretical limit, thereby significantly impeding the commercialization of perovskite LEDs. In addition, Joule heating induces ion migration and surface defects, degrades the photoluminescence quantum yield and other optoelectronic properties of perovskite films, and induces the crystallization of charge transport layers with low glass transition temperatures, resulting in LED degradation under continuous operation. Here, a novel thermally crosslinked hole transport material, poly(FCA60 -co-BFCA20 -co-VFCA20 ) (poly-FBV), with temperature-dependent hole mobility is designed, which is advantageous for balancing the charge injection of the LEDs and limiting the generation of Joule heating. The optimised CsPbI3 perovskite nanocrystal LEDs with poly-FBV realise approximately a 2-fold external quantum efficiency increase over the LED with commercial hole transport layer poly(4-butyl-phenyl-diphenyl-amine) (poly-TPD), owing to the balanced carrier injection and suppressed exciton quenching. Moreover, because of the Joule heating control provided by the novel crosslinked hole transport material, the LED utilising crosslinked poly-FBV has a 150-fold longer operating lifetime (490 min) than that utilizing poly-TPD (3.3 min). The study opens a new avenue for the use of PNC LEDs in commercial semiconductor optoelectronic devices.

Surface Modulation via Conjugated Bithiophene Ammonium Salt for Efficient Inverted Perovskite Solar Cells

The metal halide perovskite absorbers are prone to surface defects, which severely limit the power conversion efficiencies (PCEs) and the operational stability of the perovskite solar cells (PSCs). Herein, trace amounts of bithiophene propylammonium iodide (bi-TPAI) are applied to modulate the surface properties of the gas-quenched perovskite. It is found that the bi-TPAI surface treatment has negligible impact on the perovskite morphology, but it can induce a defect passivation effect and facilitate the charge carrier extraction, contributing to the gain in the open-circuit voltage (Voc) and fill factor. As a result, the PCE of the gas-quenched sputtered NiOx-based inverted PSCs is enhanced from the initial 20.0% to 22.0%. Most importantly, the bi-TPAI treatment can largely alleviate or even eliminate the burn-in process during the maximum power point tracking measurement, improving the operational stability of the devices.

Highly Effective and Efficient Self-Assembled Multilayer-Based Electrode Passivation for Operationally Stable and Reproducible Electrolyte-Gated Transistor Biosensors

To ensure the operational stability of transistor-based biosensors in aqueous electrolytes during multiple measurements, effective electrode passivation is crucially important for reliable and reproducible device performances. This paper presents a highly effective and efficient electrode passivation method using a facile solution-processed self-assembled multilayer (SAML) with excellent insulation property to achieve operational stability and reproducibility of electrolyte-gated transistor (EGT) biosensors. The SAML is created by the consecutive self-assembly of three different molecular layers of 1,10-decanedithiol, vinyl-polyhedral oligomeric silsesquioxane, and 1-octadecanethiol. This passivation enables EGT to operate stably in phosphate-buffered saline (PBS) during repeated measurements over multiple cycles without short-circuiting. The SAML-passivated EGT biosensor is fabricated with a solution-processed In2O3 thin film as an amorphous oxide semiconductor working both as a semiconducting channel in the transistor and as a functionalizable biological interface for a bioreceptor. The SAML-passivated EGT including In2O3 thin film is demonstrated for the detection of Tau protein as a biomarker of Alzheimer's disease while employing a Tau-specific DNA aptamer as a bioreceptor and a PBS solution with a low ionic strength to diminish the charge-screening (Debye length) effect. The SAML-passivated EGT biosensor functionalized with the Tau-specific DNA aptamer exhibits ultrasensitive, quantitative, and reliable detection of Tau protein from 1 × 10-15 to 1 × 10-10 M, covering a much larger range than clinical needs, via changes in different transistor parameters. Therefore, the SAML-based passivation method can be effectively and efficiently utilized for operationally stable and reproducible transistor-based biosensors. Furthermore, this presented strategy can be extensively adapted for advanced biomedical devices and bioelectronics in aqueous or physiological environments.

Protonated Organic Semiconductors: Origin of Water-Induced Charge-Trap Generation

Despite dramatic improvements in the electronic characteristics of organic semiconductors, the low operational stability of organic field-effect transistors (OFETs) hinders their direct use in practical applications. Although the literature contains numerous reports on the effects of water on the operational stability of OFETs, the underlying mechanisms of trap generation induced by water remain unclear. Here, a protonation-induced trap generation of organic semiconductors is proposed as a possible origin of the operational instability in organic field-effect transistors. Spectroscopic and electronic investigation techniques combined with simulations reveal that the direct protonation of organic semiconductors by water during operation may be responsible for the trap generation induced by bias stress; this phenomenon is independent of the trap generation at an insulator surface. In addition, the same feature occurred in small-bandgap polymers with fused thiophene rings irrespective of their crystalline ordering, implying the generality of protonation induced trap generation in various polymer semiconductors with a small bandgap. The finding of the trap-generation process provides new perspectives for achieving greater operational stability of organic field-effect transistors.

Trace Doping: Fluorine-Containing Hydrophobic Lewis Acid Enables Stable Perovskite Solar Cells

With the rapid development in perovskite solar cell (PSC), high efficiency has been achieved, but the long-term operational stability is still the most important challenges for the commercialization of this emerging photovoltaic technology. So far, bi-dopants lithium bis(trifluoromethylsulfonyl)-imide (Li-TFSI)/4-tert-butylpyridine (t-BP)-doped hole-transporting materials (HTM) have led to state-of-the art efficiency in PSCs. However, such dopants have several drawbacks in terms of stability, including the complex oxidation process, undesirable ion migration and ultra-hygroscopic nature. Herein, a fluorine-containing organic Lewis acid dopant bis(pentafluorophenyl)zinc (Zn-FP) with hydrophobic property and high migration barrier has been employed as a potential alternative to widely employed bi-dopants Li-TFSI/t-BP for poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA). The resulting Zn-FP-based PSCs achieve a maximum PCE of 20.34 % with hysteresis-free current density-voltage (J-V) scans. Specifically, the unencapsulated device exhibits a significantly advanced of operational stability under the International Summit on Organic Photovoltaic Stability protocols (ISOS-L-1), maintaining over 90 % of the original efficiency after operation for 1000 h under continuous 1-sun equivalent illumination in N2 atmosphere in both forward and reverse J-V scan.

Amorphous Fluorinated Acrylate Polymer Dielectrics for Flexible Transistors and Logic Gates with High Operational Stability

Fluorinated amorphous polymeric gate-insulating materials for organic thin-film transistors (OTFTs) not only form hydrophobic surfaces but also significantly reduce traps at the interface between the organic semiconductor and gate insulator. Therefore, these polymeric materials can enhance the OTFT's operation stability. In this study, we synthesized a new polymeric insulating material series composed of acrylate and fluorinated functional groups (with different ratios) named MBHCa-F and used them as gate insulators for OTFTs and in other applications. The insulating features of the MBHCa-F polymers, including surface energy, surface atomic content properties, dielectric constant, and leakage current, were clearly analyzed with respect to the content of the fluorinated functional groups. At higher fluorine-based functional group content, the polymeric series exhibited higher fluorine-based contents at the surface and superior electrical properties, such as field-effect mobility and driving stability, at OTFTs. Therefore, we believe that this study provides a substantial method for synthesizing polymeric insulating materials to enhance the operational stability and electrical performance of OTFTs.

Polymeric Memristor Based Artificial Synapses with Ultra-Wide Operating Temperature

Neuromorphic electronics, being inspired by how the brain works, hold great promise to the successful implementation of smart artificial systems. Among several neuromorphic hardware issues, a robust device functionality under extreme temperature is of particular importance for practical applications. Given that the organic memristors for artificial synapse applications are demonstrated under room temperature, achieving a robust device performance at extremely low or high temperature is still utterly challenging. In this work, the temperature issue is addressed by tuning the functionality of the solution-based organic polymeric memristor. The optimized memristor demonstrates a reliable performance under both the cryogenic and high-temperature environments. The unencapsulated organic polymeric memristor shows a robust memristive response under test temperature ranging from 77 to 573 K. Utilizing X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary-ion mass spectrometry (ToF-SIMS) depth profiling, the device working mechanism is unveiled by comparing the compositional profiles of the fresh and written organic polymeric memristors. A reversible ion migration induced by an applied voltage contributes to the characteristic switching behavior of the memristor. Herein, both the robust memristive response achieved at extreme temperatures and the verified device working mechanism will remarkably accelerate the development of memristors in neuromorphic systems.

Graphene-Like Conjugated Molecule as Hole-Selective Contact for Operationally Stable Inverted Perovskite Solar Cells and Modules

Further enhancing the operational lifetime of inverted-structure perovskite solar cells (PSCs) is crucial for their commercialization, and the design of hole-selective contacts at the illumination side plays a key role in operational stability. In this work, the self-anchoring benzo[rst]pentaphene (SA-BPP) is developed as a new type of hole-selective contact toward long-term operationally stable inverted PSCs. The SA-BPP molecule with a graphene-like conjugated structure shows a higher photostability and mobility than that of the frequently-used triphenylamine and carbazole-based hole-selective molecules. Besides, the anchoring groups of SA-BPP promote the formation of a large-scale uniform hole contact on ITO substrate and efficiently passivate the perovskite absorbers. Benefiting from these merits, the champion efficiencies of 22.03% for the small-sized cells and 17.08% for 5 × 5 cm² solar modules on an aperture area of 22.4 cm² are achieved based on this SA-BPP contact. Also, the SA-BPP-based device exhibits promising operational stability, with an efficiency retention of 87.4% after 2000 h continuous operation at the maximum power point under simulated 1-sun illumination, which indicates an estimated T₈₀ lifetime of 3175 h. This novel design concept of hole-selective contacts provides a promising strategy for further improving the PSC stability.

Efficient, Color-Stable, and Long-Lived White Organic Light-Emitting Diodes Utilizing Phosphorescent Molecular Aggregates

Highly efficient and stable single-stack hybrid white organic light-emitting diode (WOLED) devices are developed using two emissive layers: one with amber-colored phosphorescent molecular-aggregate emission from the Pd(II) complex, Pd(II) 7-(3-(pyridine-2-yl-κN)phenoxy-κC)(benzo-κC)([c]benzo[4,5]imidazo-κN)[1,2-a][1,5]naphthyridine, Pd3O8-Py5, and the other with blue fluorescence emission. An optimized device structure achieves high color stability under various current densities, an external quantum efficiency (EQE) of 45.5%, a power efficiency of 97.4 Lm W^-1 , and an estimated LT₉₅ (operational time to 95% of the initial luminance) of 50 744 h at an initial luminance of 1000 cd m^-2 .

Ultra-Stable and Highly Efficient White Light Emitting Diodes through CsPbBr3 Perovskite Nanocrystals-Silica Composite Phosphor Functionalized with Surface Phenyl Molecules

Poor stability of CsPbBr₃ perovskite nanocrystals (NCs) to moisture/heat/light has significantly limited their application as a green phosphor, despite their outstanding luminescent properties. Here, a remarkably stable CsPbBr₃ NCs-silica composite phosphor functionalized with surface phenyl molecules (CsPbBr₃ -SiO₂ ^Ph ) is synthesized by controlling low-temperature hydrolysis and condensation reaction of perhydropolysilazane in the presence of CsPbBr₃ NCs followed by phenyl-functionalization. Through the process, CsPbBr₃ NCs are confined in a compact silica matrix, which is impermeable to H₂ O. The synthesis strategy is extended to a classical red quantum dot, CdZnSeS@ZnS NCs, to fabricate a white light emitting diode (WLED) consisting of CsPbBr₃ -SiO₂ ^Ph and CdZnSeS@ZnS-SiO₂ ^Ph phosphor and silicone resin packaged on a commercial blue InGaN chip with luminous efficacy (LE) of 9.36 lm W^-1 . The WLED undergoes enhancements in both green and red photoluminescence over time to achieve a highly efficient performance of 38.80 lm W^-1 . More importantly, the WLED exhibits unprecedented operational stability of LE/LE₀  = 94% after 101 h-operation at 20 mA (2.56 V). The ultra-high operational stability and efficient performance are mainly attributed to thermal curing and aging through which grain growth occurs as well as deactivation of defect states by permeated atmospheric O₂ .

Boosting Perovskite Solar Cells Efficiency and Stability: Interfacial Passivation of Crosslinked Fullerene Eliminates the "Burn-in" Decay

Perovskite solar cells (PSCs) longevity is nowadays the bottleneck for their full commercial exploitation. Although lot of research is ongoing, the initial decay of the output power - an effect known as "burn-in" degradation happening in the first 100 h - is still unavoidable, significantly reducing the overall performance (typically of >20%). In this paper, the origin of the "burn-in" degradation in n-i-p type PSCs is demonstrated that is directly related to Li⁺ ions migration coming from the SnO₂ electron transporting layer visualized by time-of-flight secondary ion mass spectrometry (TOF-SIMS) measurements. To block the ion movement, a thin cross-linked [6,6]-phenyl-C61-butyric acid methyl ester layer on top of the SnO₂ layer is introduced, resulting in Li⁺ immobilization. This results in the elimination of the "burn-in" degradation, showing for the first time a zero "burn-in" loss in the performances while boosting device power conversion efficiency to >22% for triple-cation-based PSCs and >24% for formamidinium-based (FAPbI₃ ) PSCs, proving the general validity of this approach and creating a new framework for the realization of stable PSCs devices.

Strain Release and Defect Passivation in Formamidinium-Dominated Perovskite via a Novel in-Plane Thermal Gradient Assisted Crystallization Strategy

It is essential to release annealing induced strain during the crystallization process to realize efficient and stable perovskite solar cells (PSCs), which does not seem achievable using the conventional annealing process. Here we report a novel and facile thermal gradient assisted crystallization strategy by simply introducing a slant angle between the preheated hot plate and the substrate. A distinct crystallization sequence resulted along the in-plane direction pointing from the hot side to the cool side, which effectively reduced the crystallization rate, controlled the perovskite grain growth, and released the in-plane tensile strain. Moreover, this strategy enabled uniform strain distribution in the vertical direction and assisted in reducing the defects and aligning the energy bands. The corresponding device demonstrated champion power conversion efficiencies (PCEs) of 23.70% and 21.04% on the rigid and flexible substrates, respectively. These highly stable rigid devices retained 97% of the initial PCE after 1097 h of storage and more than 80% of the initial PCE after 1000 h of continuous operation at the maximum power point. This novel strategy opens a simple and effective avenue to improve the quality of perovskite films and photovoltaic devices via strain modulation and defect passivation.

Modified Polyethylene Foam for Critical Environments

One of the most important priorities for all countries with property beyond the Arctic Circle and territories located in permafrost areas is the development of special construction technologies and systems. The required conditions are met by insulation systems based on seamless insulation shells made of polyethylene foam. The study of the strength and performance properties of polyethylene foam and its combinability was carried out according to standard methods and using the methods of experimental design and the analytical processing of the results. The change in material properties at negative temperatures was determined based on the results of climatic tests, followed by an evaluation of creep under load. The evaluation of the effectiveness of the design solutions was carried out using special computer programs. It was found that the performance characteristics of products made of polyethylene foam (rolls, mats) meet the requirements for insulation materials used at temperatures down to -60 °C. The resulting material is moderately combustible, which must be taken into account when developing recommendations for its use in insulation systems. A nomogram has been developed that makes it possible to predict the properties of a material and solve formulation problems. Insulation systems were developed, and a visualisation of the thermal fields of the insulation systems of the external walls and ceilings of a building was carried out.

Stability of Perovskite Light-Emitting Diodes: Existing Issues and Mitigation Strategies Related to Both Material and Device Aspects

Metal halide perovskites combine excellent electronic and optical properties, such as defect tolerance and high photoluminescence efficiency, with the benefits of low-cost, large-area, solution-based processing. Composition- and dimension-tunable properties of perovskites have already been utilized in bright and efficient light-emitting diodes (LEDs). At the same time, there are still great challenges ahead to achieving operational and spectral stability of these devices. In this review, the origins of instability of perovskite materials, and reasons for their degradation in LEDs are considered. Then, strategies for improving the stability of perovskite materials are reviewed, such as compositional engineering, dimensionality control, defect passivation, suitable encapsulation matrices, and fabrication of core/shell perovskite nanocrystals. For improvement of the operational stability of perovskite LEDs, the use of inorganic charge-transport layers, optimization of charge balance, and proper thermal management are considered. The review is concluded with a detailed account of the current challenges and a perspective on the key approaches and opportunities on how to reach the goal of stable, bright, and efficient perovskite LEDs.

A Sub-20 nm Organic/Inorganic Hybrid Dielectric for Ultralow-Power Organic Thin-Film Transistor (OTFT) With Enhanced Operational Stability

Organic/inorganic hybrid materials are utilized extensively as gate dielectric layers in organic thin-film transistors (OTFTs). However, inherently low dielectric constant of organic materials and lack of a reliable deposition process for organic layers hamper the broad application of hybrid dielectric materials. Here, a universal strategy to synthesize high-k hybrid dielectric materials by incorporating a high-k polymer layer on top of various inorganic layers generated by different fabrication methods, including AlO_x and HfO_x , is presented. Those hybrid dielectrics commonly exhibit high capacitance (>300 nF·cm^-2 ) as well as excellent insulating properties. A vapor-phase deposition method is employed for precise control of the polymer film thickness. The ultralow-voltage (<3 V) OTFTs are demonstrated based on the hybrid dielectric layer with 100% yield and uniform electrical characteristics. Moreover, the exceptionally high stability of OTFTs for long-term operation (current change less than 5% even under 30 h of voltage stress at 2.0 MV·cm^-1 ) is achieved. The hybrid dielectric is fully compatible with various substrates, which allows for the demonstration of intrinsically flexible OTFTs on the plastic substrate. It is believed that this approach for fabricating hybrid dielectrics by introducing the high-k organic material can be a promising strategy for future low-power, flexible electronics.

Fluorination-Induced Charge Trapping and Operational Instability in Conjugated-Polymer Field-Effect Transistors

Fluorination of a conjugated polymer backbone is an effective strategy to control the microstructure and electronic structure of a conjugated polymer. Although fluorination has been widely reported to increase charge carrier mobility, its effect on the operational stability of electronic devices has not been extensively investigated. Here, the effect of fluorination of a conjugated polymer backbone on charge trapping and the operational stability of organic field-effect transistors is investigated. The results show that the device based on a fluorinated conjugated polymer exhibits relatively poor operational stability despite its greater charge carrier mobility compared with that in the device based on its nonfluorinated polymer counterpart. Experimental results reveal that the low stability originates from the greater degree of shallow trapping of charge carriers within the fluorinated polymer thin film and that the shallow trapping is closely related to the presence of minority charge carriers. A mechanism of charge trapping is proposed.

Mechanically and Ultraviolet Light Stable Ultrathin Organic Solar Cell via Semi-Embedding Silver Nanowires in a Hydrogen Bonds-Based Polyimide

Ultrathin organic solar cells (OSCs) with both high power conversion efficiency (PCE) and operational stability are of great significance for the industrial applications but still challenging. Here, we synthesized a polyimide (PI) substrate for high-performance and stable ultrathin OSCs, which was physically crosslinked via strong hydrogen bonds (denoted as HB-PI) to enhance the mechanical, thermal, solvent-resistant, and UV filtering properties (with a cut-off wavelength of 376 nm). An ultrathin flexible transparent composite electrode (FTCE, ∼7 μm) was fabricated via semi-embedding AgNWs in the HB-PI substrate. The FTCE possesses excellent optoelectronic property, smooth surface, and high mechanical stability simultaneously. Based on this FTCE, an ultrathin OSC was constructed with a PCE of 13.52% (average of 13.22%). Moreover, the ultrathin OSC showed outstanding mechanical stability (PCE decreased by less than 4% after 1000 bending cycles at a small bending radius of 0.5 mm) and superior UV light stability (no evident PCE degradation after irradiation under UV light for 10 h). This work will provide a new avenue for fabricating high-performance and stable ultrathin OSCs. This article is protected by copyright. All rights reserved.

Critical Role of Perovskite Film Stoichiometry in Determining Solar Cell Operational Stability: a Study on the Effects of Volatile A-Cation Additives

Volatile A-cation halide (AX) additives such as formamidinium chloride and methylammonium chloride have been widely employed for high-efficiency perovskite solar cells (PSCs). However, it remains unstudied how they influence the perovskite film stoichiometry and the solar cell performance and operational stability. Hereby, our work shows that over annealing of formamidinium chloride-containing perovskite films leads to a Pb-rich surface, resulting in a high initial efficiency, which however decays during maximum power point tracking (MPPT). On the contrary, perovskite films obtained by a shorter annealing time at the same temperature provide good stability during MPPT but a lower initial efficiency. Thus, we deduce that an optimal annealing is vital for both high efficiency and operational stability, which is then confirmed in the case where methylammonium chloride additive is used. With optimized perovskite annealing conditions, we demonstrate efficient and stable p-i-n PSCs that show a best power conversion efficiency of 20.7% and remain 90% of the initial performance after a 200 h MPPT at 60 °C under simulated 1 sun illumination with high UV content. Our work presents a comprehensive understanding on how volatile AX impacts perovskite film stoichiometry and its correlation to the device performance and operational stability, providing a new guideline for fabricating high-efficiency and operationally stable PSCs.

Long-Term Biocatalyst Performance: Mechanistic Prediction and Continuous Non-Isothermal Testing

The assessment of the operational stability of biocatalysts by conventional direct determination of the total turnover number (TTN), a useful indicator of lifetime biocatalyst productivity, via continuous isothermal experiments tends to be time-consuming, material-intensive, and prone to disturbances, especially in case of rather stable catalysts. In the present work, we present and validate two alternative methods for estimating the TTN of a biocatalyst for any desired operating temperature. The first method is a mechanistic approach, built upon mathematical derivation of enzyme deactivation models derived from first principles, in which TTN can be calculated from two straightforward isothermal biochemical batch measurements. The second method relies on a few non-isothermal, continuous-mode experiments in conjunction with mathematical modeling to determine the intrinsic deactivation parameters of the biocatalyst. We verify both methods on the test case of TEM-1 β-lactamase-catalyzed penicillin G (Pen G) hydrolysis. Both alternative methods provide estimates of TTN which are typically within a factor of two to five or less of the values measured directly via lengthy, costly, and error-prone conventional isothermal aging tests. Therefore, both the mechanistic approach and the non-isothermal continuous approach are extremely valuable tools to enable calculation of catalyst cost contribution in continuous processing and to eliminate underperforming candidates in search of the most stable biocatalyst.

In Situ Inorganic Ligand Replenishment Enables Bandgap Stability in Mixed-Halide Perovskite Quantum Dot Solids

Instability in mixed-halide perovskites (MHPs) is a key issue limiting perovskite solar cells and light-emitting diodes (LEDs). One form of instability arises during the processing of MHP quantum dots using an antisolvent to precipitate and purify the dots forming surface traps that lead to decreased luminescence, compromised colloidal stability, and emission broadening. Here, the introduction of inorganic ligands in the antisolvents used in dot purification is reported in order to overcome this problem. MHPs that are colloidally stable for over 1 year at 25 °C and 40% humidity are demonstrated and films that are stable under 100 W cm^-2 photoirradiation, 4× longer than the best previously reported MHPs, are reported. In LEDs, the materials enable an EQE of 24.4% (average 22.5 ± 1.3%) and narrow emission (full-width at half maximum of 30 nm). Sixfold-enhanced operating stability relative to the most stable prior red perovskite LEDs having external quantum efficiency >20% is reported.

Pressure-Assisted Space-Confinement Strategy to Eliminate PbI2 in Perovskite Layers toward Improved Operational Stability

The existence of the PbI₂ phase in the perovskite film is normally inevitable because of the easy sublimation of the organic component during the crystallization process under a relatively high annealing temperature. However, excess PbI₂ will cause significant degradation on open current voltage (V_OC) and fill factor (FF) under continuous illumination. Here, we developed a pressure-assisted space-confinement (PASC) method to enhance the phase purity of the perovskite film fabricated by the two-step spin-coating method. It was found that high pressure is more conductive to lower the sublimation rate of the organic units, and the space confinement is more favorable for the Ostwald ripening. The combination of them can easily fabricate high-quality perovskite films with large crystal grains and eliminated PbI₂ remnants. As expected, the efficiency of the solar cell was improved from 20.38 to 22.26%; more importantly, the operational stability of the corresponding device had a pronounced improvement, which remains over 85% of its initial efficiency after 500 h maximum power point tracking measurement. Based on this PASC method, a prototype PSC module (PSM) with an active area of 14 cm² was also fabricated reaching an efficiency over 17%.

Lead-Sealed Stretchable Underwater Perovskite-Based Optoelectronics via Self-Recovering Polymeric Nanomaterials

To harness the full potential of halide perovskite based optoelectronics, biological safety, compatibility with flexible/stretchable platforms, and operational stability must be guaranteed. Despite substantial efforts, none has come close to providing a solution that encompasses all of these requirements. To address these issues, we devise a multifunctional encapsulation scheme utilizing hydrogen bond-based self-recovering polymeric nanomaterials as an alternative for conventional glass-based encapsulation. We show that Pb in physically damaged halide perovskite solar cells can be completely contained within the self-recovering encapsulation upon submersion in a simulated rain bath, as indicated by in vitro cytotoxicity tests. In addition, self-recovering encapsulation accommodates stable device operation upon casual bending and even stretching, which is in stark contrast to conventional glass-based encapsulation schemes. We also demonstrate the concept of assembling user-defined scalable modular optoelectronics based on halide perovskite solar cells and light emitting diodes through the use of self-recovering conductive nanocomposites. Finally, long-term operational stability of over 1000 h was achieved under harsh accelerated conditions (50 °C/50% RH and 85 °C/0% RH) with the incorporation of an ultrathin atomic layer deposited TiO₂ barrier underneath the multifunctional encapsulation. In light of these merits, the encapsulation scheme based on self-recovering polymeric nanomaterials is proposed as a simple, but practical solution to a multifaceted challenge in the field of halide perovskites.

Efficient Planar Perovskite Solar Cells with Carbon Quantum Dot-Modified spiro-MeOTAD as a Composite Hole Transport Layer

In perovskite solar cells (PSCs), the hole-transport layer (HTL) plays an essential role in effective charge transport and extraction from the photoexcited perovskite, thus being significant for overall power conversion efficiency (PCE) and operational stability. So far, spiro-MeOTAD has been the most widely used HTL despite its inherent drawbacks, such as highly hygroscopic nature, poor conductivity, and mismatched energy-level alignment with the perovskite active layer. Here, a spiro-MeOTAD-based composite HTL modified by microwave method-synthesized carbon quantum dots (CQDs) was proposed and demonstrated as a promising HTL candidate for high-performance PSCs. The results demonstrated that the CQDs/spiro-MeOTAD composite HTL possesses several appealing characteristics for PSC applications, such as suitable energy levels for hole extraction, passivated interfacial trap states, and reduced recombination losses. Consequently, as compared to the control one using an unmodified spiro-MeOTAD HTL, (FAPbI₃)_0.95(MAPbBr₃)_0.05-based planar PSCs with composite HTL exhibit notably enhanced PCE and operational stability. Remarkably, an encouraging PCE of 20.41% was achieved for the champion device, and much improved operational stability was also demonstrated under continuous AM1.5 illumination with maximum power point (MPP) tracking conditions.

Operational Stability, Regenerability, and Thermodynamics Studies on Biogenic Silica/Magnetite/Graphene Oxide Nanocomposite-Activated Candida rugosa Lipase

Inorganic biopolymer-based nanocomposites are useful for stabilizing lipases for enhanced catalytic performance and easy separation. Herein, we report the operational stability, regenerability, and thermodynamics studies of the ternary biogenic silica/magnetite/graphene oxide nanocomposite (SiO₂/Fe₃O₄/GO) as a support for Candida rugosa lipase (CRL). The X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), field-electron scanning electron microscopy (FESEM), vibrating sample magnetometry (VSM), and nitrogen adsorption/desorption data on the support and biocatalyst corroborated their successful fabrication. XPS revealed the Fe₃O₄ adopted Fe²⁺ and Fe³⁺ oxidation states, while XRD data of GO yielded a peak at 2θ = 11.67°, with the SiO₂/Fe₃O₄/GO revealing a high surface area (≈261 m²/g). The fourier transform infrared (FTIR) spectra affirmed the successful fabricated supports and catalyst. The half-life and thermodynamic parameters of the superparamagnetic immobilized CRL (CRL/SiO₂/Fe₃O₄/GO) improved over the free CRL. The microwave-regenerated CRL/SiO₂/Fe₃O₄/GO (≈82%) exhibited higher catalytic activity than ultrasonic-regenerated (≈71%) ones. Lower activation (Ea) and higher deactivation energies (Ed) were also noted for the CRL/SiO₂/Fe₃O₄/GO (13.87 kJ/mol, 32.32 kJ/mol) than free CRL (15.26 kJ/mol, 27.60 kJ/mol). A peak at 4.28 min in the gas chromatograph-flame ionization detection (GC-FID) chromatogram of the purified ethyl valerate supported the unique six types of 14 hydrogen atoms of the ester (CAS: 539-82-2) in the proton nuclear magnetic resonance (¹H-NMR) data. The results collectively demonstrated the suitability of SiO₂/Fe₃O₄/GO in stabilizing CRL for improved operational stability and thermodynamics and permitted biocatalyst regenerability.

Triarylamine-Pyridine-Carbonitriles for Organic Light-Emitting Devices with EQE Nearly 40

Highly efficient thermally activated delayed fluorescence (TADF) molecules are in urgent demand for solid-state lighting and full-color displays. Here, the design and synthesis of three triarylamine-pyridine-carbonitrile-based TADF compounds, TPAPPC, TPAmPPC, and tTPAmPPC, are shown. They exhibit excellent photoluminescence quantum yields of 79-100% with small ΔE_ST values, fast reverse intersystem crossing (RISC), and high horizontal dipole ratios (Θ_//  = 86-88%) in the thin films leading to the enhancement of device light outcoupling. Consequently, a green organic light-emitting diode (OLED) based on TPAmPPC shows a high average external quantum efficiency of 38.8 ± 0.6%, a current efficiency of 130.1 ± 2.1 cd A^-1 , and a power efficiency of 136.3 ± 2.2 lm W^-1 . The highest device efficiency of 39.8% appears to be record-breaking among TADF-based OLEDs to date. In addition, the TPAmPPC-based device shows superior operation lifetime and high-temperature resistance. It is worth noting that the TPA-PPC-based materials have excellent optical properties and the potential for making them strong candidates for TADF practical application.

Surface Stabilization of a Formamidinium Perovskite Solar Cell Using Quaternary Ammonium Salt

Dimensionality engineering is an effective approach to improve the stability and power conversion efficiency (PCE) of perovskite solar cells (PSCs). A two-dimensional (2D) perovskite assembled from bulky organic cations to cover the surface of three-dimensional (3D) perovskite can repel ambient moisture and suppress ion migration across the perovskite film. This work demonstrates how the thermal stability of the bulky organic cation of a 2D perovskite affects the crystallinity of the perovskite and the optoelectrical properties of perovskite solar cells. Structural analysis of (FAPbI₃)_0.95(MAPbBr₃)_0.05 (FA = formamidinium ion, MA = methylammonium ion) mixed with a series of bulky cations shows a clear correlation between the structure of the bulky cations and the formation of surface defects in the resultant perovskite films. An organic cation with primary ammonium structure is vulnerable to a deprotonation reaction under typical perovskite-film processing conditions. Decomposition of the bulky cations results in structural defects such as iodide vacancies and metallic lead clusters at the surface of the perovskite film; these defects lead to a nonradiative recombination loss of charge carriers and to severe ion migration during operation of the device. In contrast, a bulky organic cation with a quaternary ammonium structure exhibits superior thermal stability and results in substantially fewer structural defects at the surface of the perovskite film. As a result, the corresponding PSC exhibits the PCE of 21.6% in a reverse current-voltage scan and a stabilized PCE of 20.1% with an excellent lifetime exceeding 1000 h for the encapsulated device under continuous illumination.

Perovskite Quantum Dots with Ultralow Trap Density by Acid Etching-Driven Ligand Exchange for High Luminance and Stable Pure-Blue Light-Emitting Diodes

The research on metal halide perovskite light-emitting diodes (PeLEDs) with green and infrared emission has demonstrated significant progress in achieving higher functional performance. However, the realization of stable pure-blue (≈470 nm wavelength) PeLEDs with increased brightness and efficiency still constitutes a considerable challenge. Here, a novel acid etching-driven ligand exchange strategy is devised for achieving pure-blue emitting small-sized (≈4 nm) CsPbBr₃ perovskite quantum dots (QDs) with ultralow trap density and excellent stability. The acid, hydrogen bromide (HBr), is employed to etch imperfect [PbBr₆ ]^4- octahedrons, thereby removing surface defects and excessive carboxylate ligands. Subsequently, didodecylamine and phenethylamine are successively introduced to bond the residual uncoordinated sites of the QDs and attain in situ exchange with the original long-chain organic ligands, resulting in near-unity quantum yield (97%) and remarkable stability. The QD-based PeLEDs exhibit pure-blue electroluminescence at 470 nm (corresponding to the Commission Internationale del'Eclairage (CIE) (0.13, 0.11) coordinates), an external quantum efficiency of 4.7%, and a remarkable luminance of 3850 cd m^-2 , which is the highest brightness reported so far for pure-blue PeLEDs. Furthermore, the PeLEDs exhibit robust durability, with a half-lifetime exceeding 12 h under continuous operation, representing a record performance value for blue PeLEDs.

Efficient and Stable Red Perovskite Light-Emitting Diodes with Operational Stability >300 h

The long-term operational stability of perovskite light-emitting diodes (PeLEDs), especially red PeLEDs with only several hours typically, has always faced great challenges. Stable β-CsPbI₃ nanocrystals (NCs) are demonstrated for highly efficient and stable red-emitting PeLEDs through incorporation of poly(maleic anhydride-alt-1-octadecene) (PMA) in synthesizing the NCs. The PMA can chemically interact with PbI₂ in the precursors via the coupling effect between O groups in PMA and Pb²⁺ to favor crystallization of stable β-CsPbI₃ NCs. Meanwhile, the cross-linked PMA significantly reduces the Pb_Cs anti-site defect on the surface of the β-CsPbI₃ NCs. Benefiting from the improved crystal phase quality, the photoluminescence quantum yield for β-CsPbI₃ NCs films remarkably increases from 34% to 89%. The corresponding red-emitting PeLEDs achieves a high external quantum efficiency of 17.8% and superior operational stability with the lifetime, the time to half the initial electroluminescence intensity (T₅₀ ) reaching 317 h at a constant current density of 30 mA cm^-2 .

Poly(N,N'-bis-4-butylphenyl-N,N'-bisphenyl)benzidine-Based Interfacial Passivation Strategy Promoting Efficiency and Operational Stability of Perovskite Solar Cells in Regular Architecture

The failure of perovskite solar cells (PSCs) to maintain their maximum efficiency over a prolonged time is due to the deterioration of the light harvesting material under environmental factors such as humidity, heat, and light. Systematically elucidating and eliminating such degradation pathways are critical to imminent commercial use of this technology. Here, a straightforward approach is introduced to reduce the level of defect-states present at the perovskite and hole transporting layer interface by treating the various perovskite surfaces with poly(N,N'-bis-4-butylphenyl-N,N'-bisphenyl)benzidine (polyTPD) molecules. This strategy significantly suppresses the defect-mediated non-radiative recombination in the ensuing devices and prevents the penetration of degrading agents into the inner layers by passivating the perovskite surface and grain boundaries. Suppressed non-radiative recombination and improved interfacial hole extraction result in PSCs with stabilized efficiency exceeding 21% with negligible hysteresis (≈19.1% for control device). Moreover, ultra-hydrophobic polyTPD passivant considerably alleviates moisture penetration, showing ≈91% retention of initial efficiencies after 300 h storage at high relative humidity of 80%. Similarly, passivated device retains 94% of its initial efficiency after 800 h under operational conditions (maximum power point tracking under continuous illumination at 60 °C). In addition to interfacial passivation function, hole-selective role of dopant-free polyTPD is also evaluated and discussed in this study.

Kilogram-Scale Crystallogenesis of Halide Perovskites for Gamma-Rays Dose Rate Measurements

Gamma-rays (γ-rays), wherever present, e.g., in medicine, nuclear environment, or homeland security, due to their strong impact on biological matter, should be closely monitored. There is a need for simple, sensitive γ-ray detectors at affordable prices. Here, it is shown that γ-ray detectors based on crystals of methylammonium lead tribromide (MAPbBr3) ideally meet these requirements. Specifically, the γ-rays incident on a MAPbBr3 crystal generates photocarriers with a high mobility-lifetime product, allowing radiation detection by photocurrent measurements at room temperatures. Moreover, the MAPbBr3 crystal-based detectors, equipped with improved carbon electrodes, can operate at low bias (≈1.0 V), hence being suitable for applications in energy-sparse environments, including space. The γ-ray detectors reported herein are exposed to radiation from a 60Co source at dose rates up to 2.3 Gy h-1 under ambient conditions for over 100 h, without any sign of degradation. The excellent radiation tolerance stems from the intrinsic structural plasticity of the organic-inorganic halide perovskites, which can be attributed to a defect-healing process by fast ion migration at the nanoscale level. The sensitivity of the γ-ray detection upon volume is tested for MAPbBr3 crystals reaching up to 1000 cm3 (3.3 kg in weight) grown by a unique crystal growth technique.

Tailoring the Electronic Landscape of Quantum Dot Light-Emitting Diodes for High Brightness and Stable Operation

The charge injection imbalance into the quantum dot (QD) emissive layer of QD-based light-emitting diodes (QD-LEDs) is an unresolved issue that is detrimental to the efficiency and operation stability of devices. Herein, an integrated approach to harmonize the charge injection rates for bright and stable QD-LEDs is proposed. Specifically, the electronic characteristics of the hole transport layer (HTL) is delicately designed in order to facilitate the hole injection from the HTL into QDs and confine the electron overflow toward the HTL. The well-defined exciton recombination zone by the engineered QDs and HTL results in high performance with a peak luminance exceeding 410 000 cd/m², suppressed efficiency roll-off characteristics (ΔEQE < 5% between 200 and 200 000 cd/m²), and prolonged operational stability. The electric and optoelectronic analyses reveal the charge carrier injection mechanism at the interface between the HTL and QDs and provides the design principle of QD heterostructures and charge transport layers for high-performance QD-LEDs.

Design Strategy Towards Horizontally Oriented Luminescent Tetradentate-Ligand-Containing Gold(III) Systems

Phosphorescent dopants are promising candidates for organic light-emitting diodes (OLEDs). Although it has been established that the out-coupling efficiency and overall performances of vacuum-deposited OLEDs can be significantly improved by a horizontal orientation of the dopants, no horizontally oriented gold(III) complexes have been reported to date. Herein, a novel class of tetradentate C^C^N^N ligand-containing gold(III) complexes with a preferential horizontal orientation successfully generated through a one-pot reaction is reported. These complexes demonstrate high photoluminescence quantum yields of 70 % and a high horizontal dipole ratio of 0.87 in solid-state thin films. Green-emitting OLEDs based on these complexes operate with a maximum external quantum efficiency of 20.6 % with an estimated out-coupling efficiency of around 30 %. A promising device stability has been achieved in the vacuum-deposited OLEDs, with operational half-lifetimes of around 37 500 h at 100 cd m^-2 .

Continuous Production of Galacto-Oligosaccharides by an Enzyme Membrane Reactor Utilizing Free Enzymes

Galacto-oligosaccharides (GOS) are prebiotic compounds widely used for their health-promoting effects. Conventionally, GOS is produced by the enzymatic conversion of lactose in stirred tank reactors (STR). The high operational costs associated with enzyme inactivation and removal might be reduced by the application of enzyme membrane reactors (EMR). In this study, we aimed to assess the potential of continuous GOS production by EMR using soluble Biolacta N5, a Bacillus circulans-derived commercial enzyme preparation. The steady-state performance of the EMR equipped with an ultrafiltration module was investigated as function of residence time (1.1-2.8 h) and enzyme load (17-190 U·g^-1) under fixed operational settings of temperature (50 °C), pH (6.0), lactose feed concentration (300 g·kg^-1), and recirculation flow-rate (0.18 m³·h^-1). Results indicate that the yield of oligosaccharides with higher degree of polymerization (DP3-6) in STR (approx. 38% on total carbohydrate basis) exceeds that measured in EMR (ranging from 24% to 33%). However, a stable catalytic performance without a significant deterioration in product quality was observed when operating the EMR for an extended period of time (> 120 h). Approx. 1.4 kg of DP3-6 was produced per one gram of crude enzyme preparation over the long-term campaigns, indicating that EMR efficiently recovers enzyme activity.

Inverse Growth of Large-Grain-Size and Stable Inorganic Perovskite Micronanowire Photodetectors

Control of forward and inverse reactions between perovskites and precursor materials is key to attaining high-quality perovskite materials. Many techniques focus on synthesizing nanostructured CsPbX₃ materials (e.g., nanowires) via a forward reaction (CsX + PbX₂ → CsPbX₃). However, low solubility of inorganic perovskites and complex phase transition make it difficult to realize the precise control of composition and length of nanowires using the conventional forward approach. Herein, we report the self-assembly inverse growth of CsPbBr₃ micronanowires (MWs) (CsPb₂Br₅ → CsPbBr₃ + PbBr₂↑) by controlling phase transition from CsPb₂Br₅ to CsPbBr₃. The two-dimensional (2D) structure of CsPb₂Br₅ serves as nucleation sites to induce initial CsPbBr₃ MW growth. Also, phase transition allows crystal rearrangement and slows down crystal growth, which facilitates the MW growth of CsPbBr₃ crystals along the 2D planes of CsPb₂Br₅. A CsPbBr₃ MW photodetector constructed based on the inverse growth shows a high responsivity of 6.44 A W^-1 and detectivity of ∼10¹² Jones. Large grain size, high crystallinity, and large thickness can effectively alleviate decomposition/degradation of perovskites, which leads to storage stability for over 60 days in humid environment (relative humidity = 45%) and operational stability for over 3000 min under illumination (wavelength = 400 nm, light intensity = 20.06 mW cm^-2).

The Role of Reverse Intersystem Crossing Using a TADF-Type Acceptor Molecule on the Device Stability of Exciplex-Based Organic Light-Emitting Diodes

Exciplex system exhibiting thermally activated delayed fluorescence (TADF) holds a considerable potential to improve organic light-emitting diode (OLED) performances. However, the operational lifetime of current exciplex-based devices, unfortunately, falls far behind the requirement for commercialization. Herein, rationally choosing a TADF-type electron acceptor molecule is reported as a new strategy to enhance OLEDs' operating lifetime. A comprehensive study of the exciplex system containing 9,9',9''-triphenyl-9H,9'H,9''H-3,3':6',3''-tercarbazole (Tris-PCz) and triazine (TRZ) derivatives clarifies the relationship between unwanted carrier recombination on acceptor molecules, TADF property of acceptors, and the device degradation event. By employing a proposed "exciton recycling" strategy, a threefold increased operational lifetime can be achieved while still maintaining high-performance OLED properties. In particular, a stable blue OLED that employs this strategy is successfully demonstrated. This research provides an important step for exciplex-based devices toward the significant improvement of operational stability.

Tailored Amphiphilic Molecular Mitigators for Stable Perovskite Solar Cells with 23.5% Efficiency

Passivation of interfacial defects serves as an effective means to realize highly efficient and stable perovskite solar cells (PSCs). However, most molecular modulators currently used to mitigate such defects form poorly conductive aggregates at the perovskite interface with the charge collection layer, impeding the extraction of photogenerated charge carriers. Here, a judiciously engineered passivator, 4-tert-butyl-benzylammonium iodide (tBBAI), is introduced, whose bulky tert-butyl groups prevent the unwanted aggregation by steric repulsion. It is found that simple surface treatment with tBBAI significantly accelerates the charge extraction from the perovskite into the spiro-OMeTAD hole-transporter, while retarding the nonradiative charge carrier recombination. This boosts the power conversion efficiency (PCE) of the PSC from ≈20% to 23.5% reducing the hysteresis to barely detectable levels. Importantly, the tBBAI treatment raises the fill factor from 0.75 to the very high value of 0.82, which concurs with a decrease in the ideality factor from 1.72 to 1.34, confirming the suppression of radiation-less carrier recombination. The tert-butyl group also provides a hydrophobic umbrella protecting the perovskite film from attack by ambient moisture. As a result, the PSCs show excellent operational stability retaining over 95% of their initial PCE after 500 h full-sun illumination under maximum-power-point tracking under continuous simulated solar irradiation.

Surface-2D/Bulk-3D Heterophased Perovskite Nanograins for Long-Term-Stable Light-Emitting Diodes

Although metal halide perovskite (MHP) light-emitting diodes (LEDs) have demonstrated great potential in terms of electroluminescence efficiency, the operational stability of MHP LEDs currently remains the biggest bottleneck toward their practical usage. Well-confined excitons/charge carriers in a dielectric/quantum well based on conventional spatial or potential confinement approaches substantially enhance radiative recombination in MHPs, but an increased surface-to-volume ratio and multiphase interfaces likely result in a high degree of surface or interface defect states, which brings about a critical environmentally/operationally vulnerable point on LED stability. Here, an effective solution is suggested to mitigate such drawbacks using strategically designed surface-2D/bulk-3D heterophased MHP nanograins for long-term-stable LEDs. The 2D surface-functionalized MHP renders significantly reduced trap density, environmental stability, and an ion-migration-immune surface in addition to a fast radiative recombination owing to its spatially and potentially confined charge carriers, simultaneously. As a result, heterophased MHP LEDs show substantial improvement in operational lifetime (T₅₀ : >200 h) compared to conventional pure 3D or quasi-2D counterparts (T₅₀ : < 0.2 h) as well as electroluminescence efficiency (surface-2D/bulk-3D: ≈7.70 ph per el% and pure 3D: ≈0.46 ph per el%).

Inorganic CuFeO2 Delafossite Nanoparticles as Effective Hole Transport Materials for Highly Efficient and Long-Term Stable Perovskite Solar Cells

The regular architecture (n-i-p) of perovskite solar cells (PSCs) has attracted increasing interest in the renewable energy field, owing to high certified efficiencies in the recent years. However, there are still serious obstacles of PSCs associated with spiro-OMeTAD hole transport material (HTM), such as (i) prohibitively expensive material cost (∼150-500 $/g) and (ii) operational instability at elevated temperatures and high humidity levels. Herein, we have reported the highly photo, thermal, and moisture-stable and cost-effective PSCs employing inorganic CuFeO₂ delafossite nanoparticles as a HTM layer, for the first time. By exhibiting superior hole mobility and additive-free nature, the best-performing cell achieved a power conversion efficiency (PCE) of 15.6% with a negligible hysteresis. Despite exhibiting a lower PCE as compared to the spiro-OMeTAD-based control cell (19.1%), nonencapsulated CuFeO₂-based cells maintained above 85% of their initial efficiency, while the PCE of control cells dropped to ∼10% under continuous illumination at maximum power point tracking after 1000 h. More importantly, the performance of control cells was quickly degraded at above 70 °C, whereas CuFeO₂-based cells, retaining ∼80% of their initial efficiency after 200 h, were highly stable even at 85 °C in ambient air under dark conditions. Besides showing significant improvement in stability against light soaking and thermal stress, CuFeO₂-based cells exhibited superior shelf stability even at 80 ± 5% relative humidity and retained over 90% of their initial PCE. Overall, we strongly believe that this study highlights the potential of inorganic HTMs for the commercial deployment of long-term stable and low-cost PSCs.

"Positive Incentive" Approach To Enhance the Operational Stability of Quantum Dot-Based Light-Emitting Diodes

Balanced charge injection promises high efficiency of quantum dot-based light-emitting diodes (QD-LEDs). The most widely used approach to realize charge injection balance impedes the injection rate of the dominant charge carrier with energetic barriers. However, these approaches often accompany unwanted outcomes (e.g., the increase in operation voltage) that sacrifice the operational stability of devices. Herein, a "positive incentive" approach is proposed to enhance the efficiency and the operational stability of QD-LEDs. Specifically, the supply of hole, an inferior carrier than its counterpart, is facilitated by adopting a thin fullerene (C₆₀) interlayer at the interface between the hole injection layer (MoO_X) and hole transport layer (4,4'-bis(9-carbazolyl)-1,1'-biphenyl). The C₆₀ interlayer boosts the hole current by eliminating the universal energy barrier, lowers the operation voltage of QD-LEDs, and enhances the charge balance in the QD emissive layer within the working device. Consequently, QD-LEDs benefitting from the adoption of the C₆₀ interlayer exhibit significantly enhanced device efficiency and operation stability. Grounded on the quantitative assessment of the charge injection imbalance within the QD emissive layer, the impact of electrical parameters of QD-LEDs on their optoelectronic performance and operational stability is also discussed.

Spontaneous Generation of a Molecular Thin Hydrophobic Skin Layer on a Sub-20 nm, High-k Polymer Dielectric for Extremely Stable Organic Thin-Film Transistor Operation

Polymer dielectric materials with hydroxyl functionalities such as poly(4-vinylphenol) and poly(vinyl alcohol) have been utilized widely in organic thin-film transistors (OTFTs) because of their excellent insulating performance gained by hydroxyl-mediated cross-linking. However, the polar hydroxyl functionality also deleteriously affects the performance of OTFTs and significantly impairs the device stability. In this study, a sub-20 nm, high-k copolymer dielectric with hydroxyl functionality, poly(2-hydroxyethyl acrylate-co-di(ethylene glycol) divinyl ether), was synthesized in the vapor phase via initiated chemical vapor deposition. The inherently dry environment offered by the vapor-phase polymer synthesis prompted the snuggling of polar hydroxyl functionalities into the bulk polymer film to form a molecular thin hydrophobic skin layer at its surface, verified by near-edge X-ray absorption fine structure analysis. The chemical composition of the copolymer dielectric was optimized systematically to achieve high dielectric constant (k ≈ 6.2) as well as extremely low leakage current densities (less than 3 × 10^-8 A/cm² in the range of ±2 MV/cm) even with sub-20 nm thickness, leading to one of the highest capacitance (higher than 300 nF/cm²) achieved by a single polymer dielectric to date. Exploiting the structural advantage of the cross-linked high-k polymer dielectric, high-performance OTFTs were obtained. Notably, the spontaneously formed molecular thin, hydrophobic skin layer in the copolymer film substantially suppressed the hysteresis in the transistor operation. The trap analysis also suggested the formation of bulk trap with a high energy barrier and sufficiently low trap densities at the semiconductor/dielectric interface, owing to the surface skin layer. Furthermore, the OTFTs with the -OH-containing copolymer dielectric showed an unprecedentedly excellent operational stability. No apparent OTFT degradation was observed up to 50 000 s of high constant voltage stress (corresponding to the applied electric field of 1.4 MV/cm) because of the markedly suppressed interfacial trap density by the hydrophobic skin layer, together with the current compensation by the bulk hydroxyl functionalities. We believe that the surface modification-free, one-step polymer dielectric synthetic strategy will provide a new insight into the design of polymer dielectric materials for high-performance, low-power soft electronic devices with high operational stability.