Efficient and stable inverted perovskite solar cells with very high fill factors via incorporation of star-shaped polymer

Bottom-Up Defect Modification Through Oily-Allicin Modified Buried Interface Achieving Highly Efficient and Stable Perovskite Solar Cells

The buried interface properties of the perovskite solar cells (PSCs) play a crucial role in the power conversion efficiency (PCE) and operational stability. The metal-oxide/perovskite heterogeneous interfaces are highly defective and cause serious ion migration. However, the buried and unexposed bottom interface and simultaneous stabilization of grain boundaries receive less attention and effective solutions. To tackle this problem, a solid-liquid strategy is employed by introducing oily-additive allicin at the buried interface to passivate the shallow (VI and Vo) and deep traps (VPb and PbI). Interestingly, oily status allicin fills the pinholes at the heterointerface and wraps the perovskite grains, suppressing the ion migration during the photoaging process. As a result, an outstanding PCE of 25.07% is achieved with a remarkable fill factor (FF) of 84.03%. The modified devices can maintain 94.51% of the original PCE after light soaking under 1-sun illumination for 1000 h. This work demonstrates a buried interface modification method that employs an eco-friendly additive, which helps promote the development of PSCs with high performance and stability.

Minimizing Interfacial Energy Loss and Volatilization of Formamidinium via Polymer-Assisted D-A supramolecular Self-Assembly Interface for Inverted Perovskite Solar Cells with 25.78% Efficiency

2D perovskite passivation strategies effectively reduce defect-assisted carrier nonradiative recombination losses on the perovskite surface. Nonetheless, severe energy losses are causing by carrier thermalization, interfacial nonradiative recombination, and conduction band offset still persist at heterojunction perovskite/PCBM interfaces, which limits further performance enhancement of inverted heterojunction PSCs. Here, 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (5FTPP) is introduced between 3D/2D perovskite heterojunction and PCBM. Compared to tetraphenylporphyrin without electron-withdrawing fluoro-substituents, 5FTPP can self-assemble with PCBM at interface into donor-acceptor (D-A) complex with stronger supramolecular interaction and lower energy transfer losses. This rapid energy transfer from donor (5FTPP) to acceptor (PCBM) within femtosecond scale is demonstrated to enlarge hot carrier extraction rates and ranges, reducing thermalization losses. Furthermore, the incorporation of polystyrene derivative (PD) reinforces D-A interaction by inhibiting self-π-π stacking of 5FTPP, while fine-tuning conduction band offset and suppressing interfacial nonradiative recombination via Schottky barrier, dipole, and n-doping. Notably, the multidentate anchoring of PD-5FTPP with FA+, Pb2+, and I- mitigates the adverse effects of FA+ volatilization during thermal stress. Ultimately, devices with PD-5FTPP achieve a power conversion efficiency of 25.78% (certified: 25.36%), maintaining over 90% of initial efficiency after 1000 h of continuous illumination at the maximum power point (65 °C) under ISOS-L-2 protocol.

Bilateral Chemical Linking at NiOx Buried Interface Enables Efficient and Stable Inverted Perovskite Solar Cells and Modules

Inverted NiOx-based perovskite solar cells (PSCs) exhibit considerable potential because of their low-temperature processing and outstanding excellent stability, while is challenged by the carriers transfer at buried interface owing to the inherent low carrier mobility and abundant surface defects that directly deteriorates the overall device fill factor. Present work demonstrates a chemical linker with the capability of simultaneously grasping NiOx and perovskite crystals by forming a Ni-S-Pb bridge at buried interface to significantly boost the carriers transfer, based on a rationally selected molecule of 1,3-dimethyl-benzoimidazol-2-thione (NCS). The constructed buried interface not only reduces the pinholes and needle-like residual PbI2 at the buried interface, but also deepens the work function and valence band maximum positions of NiOx, resulting in a smaller VBM offset between NiOx and perovskite film. Consequently, the modulated PSCs achieved a high fill factor up to 86.24 %, which is as far as we know the highest value in records of NiOx-based inverted PSCs. The NCS custom-tailored PSCs and minimodules (active area of 18 cm2) exhibited a champion efficiency of 25.05 % and 21.16 %, respectively. The unencapsulated devices remains over 90 % of their initial efficiency at maximum power point under continuous illumination for 1700 hours.

Realizing Stable Perovskite Solar Cells with Efficiency Exceeding 25.6% Through Crystallization Kinetics and Spatial Orientation Regulation

Organic-inorganic hybrid perovskites have emerged as highly promising candidates for photovoltaic applications, owing to the exceptional optoelectronic properties and low cost. Nonetheless, the performance and stability of solar cells suffer from the defect states of perovskite films aroused by non-optically active phases and non-centralized crystal orientation. Herein, a versatile organic molecule, Hydantoin, to modulate the crystallization of perovskite, is developed. Benefiting from the diverse functional groups, more spatially oriented perovskite films with high crystallinity are formed. This enhancement is accompanied by a conspicuous reduction in defect density, yielding efficiency of 25.66% (certified 25.15%), with superb environmental stability. Notably, under the standard measurement conditions (ISOS-L-1I), the maximum power point (MPP) output maintains 96.8% of the initial efficiency for 1600 h and exhibits excellent ion migration suppression. The synergistic regulation of crystallization and spatial orientation offers novel avenues for propelling perovskite solar cell (PSC) development.

Instability of Formamidinium Lead Iodide (FAPI) Deposited on a Copper Oxide Hole Transporting Layer (HTL)

Copper oxide appears to be a promising candidate for a hole transport layer (HTL) in emerging perovskite solar cells. Reasons for this are its good optical and electrical properties, cost-effectiveness, and high stability. However, is this really the case? In this study, we demonstrate that copper oxide, synthesized by a spray-coating method, is unstable in contact with formamidinium lead triiodide (FAPI) perovskite, leading to its decomposition. Using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible (UV-vis) spectrophotometry, we find that the entire copper oxide diffuses into and reacts with the FAPI film completely. The reaction products are an inactive yellow δ-FAPI phase, copper iodide (CuI), and an additional new phase of copper formate hydroxide (CH2CuO3) that has not been reported previously in the literature.

Highly Efficient and Scalable p-i-n Perovskite Solar Cells Enabled by Poly-metallocene Interfaces

Inverted p-i-n perovskite solar cells (PSCs) are easy to process but need improved interface characteristics with reduced energy loss to prevent efficiency drops when increasing the active photovoltaic area. Here, we report a series of poly ferrocenyl molecules that can modulate the perovskite surface enabling the construction of small- and large-area PSCs. We found that the perovskite-ferrocenyl interaction forms a hybrid complex with enhanced surface coordination strength and activated electronic states, leading to lower interfacial nonradiative recombination and charge transport resistance losses. The resulting PSCs achieve an enhanced efficiency of up to 26.08% for small-area devices and 24.51% for large-area devices (1.0208 cm2). Moreover, the large-area PSCs maintain >92% of the initial efficiency after 2000 h of continuous operation at the maximum power point under 1-sun illumination and 65 °C.

Stabilizing Top Interface by Molecular Locking Strategy with Polydentate Chelating Biomaterials toward Efficient and Stable Perovskite Solar Cells in Ambient Air

The instability of top interface induced by interfacial defects and residual tensile strain hinders the realization of long-term stable n-i-p regular perovskite solar cells (PSCs). Herein, one molecular locking strategy is reported to stabilize top interface by adopting polydentate ligand green biomaterial 2-deoxy-2,2-difluoro-d-erythro-pentafuranous-1-ulose-3,5-dibenzoate (DDPUD) to manipulate the surface and grain boundaries of perovskite films. Both experimental and theoretical evidence collectively uncover that the uncoordinated Pb2+ ions, halide vacancy, and/or I─Pb antisite defects can be effectively healed and locked by firm chemical anchoring on the surface of perovskite films. The ingenious polydentate ligand chelating is translated into reduced interfacial defects, increased carrier lifetimes, released interfacial stress, and enhanced moisture resistance, which should be liable for strengthened top interface stability and inhibited interfacial nonradiative recombination. The universality of the molecular locking strategy is certified by employing different perovskite compositions. The DDPUD modification achieves an enhanced power conversion efficiency (PCE) of 23.17-24.47%, which is one of the highest PCEs ever reported for the devices prepared in ambient air. The unsealed DDPUD-modified devices maintain 98.18% and 88.10% of their initial PCEs after more than 3000 h under a relative humidity of 10-20% and after 1728 h at 65 °C, respectively.

Crystallization Regulation and Lead Leakage Prevention Simultaneously for High-Performance CsPbI2Br Perovskite Solar Cells

All-inorganic CsPbI2Br perovskite is striking as a result of the reasonable band gap and thermal stability. However, the notorious air instability, unsatisfactory conversion efficiencies, and toxic water-soluble Pb2+ ions have greatly limited the further development of CsPbI2Br-based devices. Herein, a facile strategy is developed to prepare efficient and air-stable CsPbI2Br-based perovskite solar cells (PSCs) with in situ lead leakage protection. With the introduction of 2,2'-dihydroxy-4,4'-dimethoxy-5,5'-disulfobenzophenone disodium salt (BP-9) into the CsPbI2Br precursor solution, the crystallization of perovskite can be regulated at a reduced trap density, the uncoordinated Pb2+ ions and electron-rich defects in the structure can be passivated to suppress non-radiative recombination, and the energy level arrangement can be optimized to improve charge carrier transport. Consequently, the optimized PSC achieved a championship efficiency of 17.11%, accompanied by negligible J-V hysteresis and remarkably improved air stability. More importantly, the strong chelation of BP-9 with water-soluble Pb2+ ions minimizes the leakage of toxic lead in the perovskite structure.

Enhancing Ultraviolet Stability and Performance of Wide Bandgap Perovskite Solar Cells Through Ultraviolet Light-Absorbing Passivator

Ultraviolet light (UV) has caused tremendous damage to perovskite solar cells (PSCs), degrading the perovskite and shortening their lifetime. Defects act as non-radiative recombination sites, accelerate the degradation process, reduce the efficiency of the device and weaken the stability of solar cell. In this work, to realize efficient and stable p-i-n wide bandgap solar cells under UV, a synergetic strategy utilizing UV light-absorbing passivator, (Trifluoroacetyl) benzotriazole (TFABI), enhance UV photostability and regulate the defect passivation is proposed. By using TFABI, the degradation of the perovskite absorption layer under UV light is suppressed, spectral response is enhanced and the Pb vacancy defects are passivated. As a result, the target device achieves an efficiency of 21.54%, exhibiting excellent long-term stability under 365 nm UV irradiation. After 60 h of irradiation, it retains 85% of its initial value (60 mW cm-2 , RH 25-30%, 25 °C).

Interfacial Layer Materials with a Truxene Core for Dopant-Free NiOx -Based Inverted Perovskite Solar Cells

Nickel oxide (NiOx ) is commonly used as a holetransporting material (HTM) in p-i-n perovskite solar cells. However, the weak chemical interaction between the NiOx and CH3 NH3 PbI3 (MAPbI3 ) interface results in poor crystallinity, ineffective hole extraction, and enhanced carrier recombination, which are the leading causes for the limited stability and power conversion efficiency (PCE). Herein, two HTMs, TRUX-D1 (N2 ,N7 ,N12 -tris(9,9-dimethyl-9H-fluoren-2-yl)-5,5,10,10,15,15-hexaheptyl-N2 ,N7 ,N12 -tris(4-methoxyphenyl)-10,15-dihydro-5H-diindeno[1,2-a:1',2'-c]fluorene-2,7,12-triamine) and TRUX-D2 (5,5,10,10,15,15-hexaheptyl-N2 ,N7 ,N12 -tris(4-methoxyphenyl)-N2 ,N7 ,N12 -tris(10-methyl-10H-phenothiazin-3-yl)-10,15-dihydro-5H-diindeno[1,2-a:1',2'-c]fluorene-2,7,12-triamine), are designed with a rigid planar C3 symmetry truxene core integrated with electron-donating amino groups at peripheral positions. The TRUX-D molecules are employed as effective interfacial layer (IFL) materials between the NiOx and MAPbI3 interface. The incorporation of truxene-based IFLs improves the quality of perovskite crystallinity, minimizes nonradiative recombination, and accelerates charge extraction which has been confirmed by various characterization techniques. As a result, the TRUX-D1 exhibits a maximum PCE of up to 20.8% with an impressive long-term stability. The unencapsulated device retains 98% of their initial performance following 210 days of aging in a glove box and 75.5% for the device after 80 days under ambient air condition with humidity over 40% at 25 °C.

Moisture-Resilient Perovskite Solar Cells for Enhanced Stability

With the rapid rise in device performance of perovskite solar cells (PSCs), overcoming instabilities under outdoor operating conditions has become the most crucial obstacle toward their commercialization. Among stressors such as light, heat, voltage bias, and moisture, the latter is arguably the most critical, as it can decompose metal-halide perovskite (MHP) photoactive absorbers instantly through its hygroscopic components (organic cations and metal halides). In addition, most charge transport layers (CTLs) commonly employed in PSCs also degrade in the presence of water. Furthermore, photovoltaic module fabrication encompasses several steps, such as laser processing, subcell interconnection, and encapsulation, during which the device layers are exposed to the ambient atmosphere. Therefore, as a first step toward long-term stable perovskite photovoltaics, it is vital to engineer device materials toward maximizing moisture resilience, which can be accomplished by passivating the bulk of the MHP film, introducing passivation interlayers at the top contact, exploiting hydrophobic CTLs, and encapsulating finished devices with hydrophobic barrier layers, without jeopardizing device performance. Here, existing strategies for enhancing the performance stability of PSCs are reviewed and pathways toward moisture-resilient commercial perovskite devices are formulated.

Iodide manipulation using zinc additives for efficient perovskite solar minimodules

Interstitial iodides are the most critical type of defects in perovskite solar cells that limits efficiency and stability. They can be generated during solution, film, and device processing, further accelerating degradation. Herein, we find that introducing a small amount of a zinc salt- zinc trifluoromethane sulfonate (Zn(OOSCF3)2) in the perovskite solution can control the iodide defects in resultant perovskites ink and films. CF3SOO̶ vigorously suppresses molecular iodine formation in the perovskites by reducing it to iodide. At the same time, zinc cations can precipitate excess iodide by forming a Zn-Amine complex so that the iodide interstitials in the resultant perovskite films can be suppressed. The perovskite films using these additives show improved photoluminescence quantum efficiency and reduce deep trap density, despite zinc cations reducing the perovskite grain size and iodide interstitials. The zinc additives facilitate the formation of more uniform perovskite films on large-area substrates (78-108 cm2) in the blade-coating process. Fabricated minimodules show power conversion efficiencies of 19.60% and 19.21% with aperture areas of 84 and 108 cm2, respectively, as certified by National Renewable Energy Laboratory (NREL), the highest efficiency certified for minimodules of these sizes.

Diffusible Capping Layer Enabled Homogeneous Crystallization and Component Distribution of Hybrid Sequential Deposited Perovskite

Nowadays, the development of wide-bandgap perovskite by thermal evaporation and spin-coating hybrid sequential deposition (HSD) method has special meaning on textured perovskite/silicon tandem solar cells. However, the common issues of insufficient reaction caused by blocking of perovskite capping layer are exacerbated in HSD, because evaporated precursors are usually denser with higher crystallinity and the widely used additive-assisted microstructure is also difficult to access. Here, a facile "diffusible perovskite capping layer" (DPCL) strategy to solve this dilemma is presented. With DPCL, crystallization alleviation of perovskite and more diffusion channels of organic salts can be realized simultaneously, contributing to a homogenization process. The resultant perovskite films exhibit complete conversion, uniform crystallization, enhanced quality, and reduced defect, leading to obvious improvements in device efficiency, repeatability, and stability. This work offers a way to promote the development of textured tandems a step further.

Development on inverted perovskite solar cells: A review

Recently, inverted perovskite solar cells (IPSCs) have received note-worthy consideration in the photovoltaic domain because of its dependable operating stability, minimal hysteresis, and low-temperature manufacture technique in the quest to satisfy global energy demand through renewable means. In a decade transition, perovskite solar cells in general have exceeded 25 % efficiency as a result of superior perovskite nanocrystalline films obtained via low temperature synthesis methods along with good interface and electrode materials management. This review paper presents detail processes of refining the stability and power conversion efficiencies in IPSCs. The latest development in the power conversion efficiency, including structural configurations, prospect of tandem solar cells, mixed cations and halides, films' fabrication methods, charge transport material alterations, effects of contact electrode materials, additive and interface engineering materials used in IPSCs are extensively discussed. Additionally, insights on the state of the art and IPSCs' continued development towards commercialization are provided.

Improved Air Stability for High-Performance FACsPbI3 Perovskite Solar Cells via Bonding Engineering

Despite the fact that perovskite solar cells (PSCs) are widely popular due to their superb power conversion efficiency (PCE), their further applications are still restricted by low stability and high-density defects. Especially, the weak binding and ion-electron properties of perovskite crystals make them susceptible to moisture attack under environmental stress. Herein, we report an overall sulfidation strategy via introduction of 1-pentanethiol (PT) into the perovskite film to inhibit bulk defects and stabilize Pb ions. It has been confirmed that the thiol groups in PT can stabilize uncoordinated Pb ions and passivate iodine vacancy defects by forming strong Pb-S bonds, thus reducing nonradiative recombination. Moreover, the favorable passivation process also optimizes the energy-level arrangement, induces better perovskite crystallization, and enhances the charge extraction in the full solar cells. Consequently, the PT-modified inverted device delivers a champion PCE of 22.46%, which is superior to that of the control device (20.21%). More importantly, the PT-modified device retains 91.5% of its initial PCE after storage in air for 1600 h and over 85% of its initial PCE after heating at 85 °C for 800 h. This work provides a new perspective to simultaneously improve the performance and stability of PSCs to satisfy their commercial applications.

Perovskite Solar Cells Based on Polymerized Chlorophyll Films as Environmentally Friendly Hole-Transporting Layers

Hole-transporting layers (HTLs) play a crucial role in the performance of inverted, p-i-n perovskite solar cells (PSCs). Chlorophylls (Chls) are naturally abundant organic photoconductors on earth, with good charge carrier mobility and appropriate Fermi energy levels that make them promising candidates for use in photovoltaic devices. However, Chls films prepared using the solution method exhibit lower carrier mobility compared to other organic polymer films, which limits their application in PSCs. To address this issue, Chls molecules are chemically linked to reduce the charge transfer barrier, thus the transfer of charges between molecules is transformed to intramolecular charge transfer. This study synthesizes and characterizes two polymerized Chl films, PolyCuChl and PolyNiChl, as HTLs of CH3 NH3 PbI3 -based PSCs. PSCs based on the electrochemical polymerization of PolyChl HTLs demonstrate an enhanced power conversion efficiency (PCE) of up to 19.0%, which is the highest efficiency among devices based on Chl materials. Furthermore, these devices demonstrated exceptional long-term stability. These results highlight the potential of polymerized Chl films as a viable alternative to conventional HTLs in PSCs. The approach utilizes abundant, environmentally friendly, and versatile Chl derivatives, and can be extended to develop next-generation HTL materials for improved PSC performance.

Characterizing Spatial and Energetic Distributions of Trap States Toward Highly Efficient Perovskite Photovoltaics

Due to their greater opt electric performance, perovskite photovoltaics (PVs) present huge potential to be commercialized. Perovskite PV's high theoretical efficiency expands the available development area. The passivation of defects in perovskite films is crucial for approaching the theoretical limit. In addition to creating efficient passivation techniques, it is essential to direct the passivation approach by getting precise and real-time information on the trap states through measurements. Therefore, it is necessary to establish quantitative characterization methods for the trap states in energy and 3D spaces. The authors cover the characterization of the spatial and energy distributions of trap states in this article with an eye toward high-efficiency perovskite photovoltaics. After going over the strategies that have been created for characterizing and evaluating trap states, the authors will concentrate on how to direct the creative development of characterization techniques for trap states assessment and highlight the opportunities and challenges of future development. The 3D space and energy distribution mappings of trap states are anticipated to be realized. The review will give key guiding importance for further approaching the theoretical efficiency of perovskite photovoltaics, offering some future research direction and technological assistance for the development of appropriate targeted passivation technologies.

Homogenizing out-of-plane cation composition in perovskite solar cells

Perovskite solar cells with the formula FA1-xCsxPbI3, where FA is formamidinium, provide an attractive option for integrating high efficiency, durable stability and compatibility with scaled-up fabrication. Despite the incorporation of Cs cations, which could potentially enable a perfect perovskite lattice1,2, the compositional inhomogeneity caused by A-site cation segregation is likely to be detrimental to the photovoltaic performance of the solar cells3,4. Here we visualized the out-of-plane compositional inhomogeneity along the vertical direction across perovskite films and identified the underlying reasons for the inhomogeneity and its potential impact for devices. We devised a strategy using 1-(phenylsulfonyl)pyrrole to homogenize the distribution of cation composition in perovskite films. The resultant p-i-n devices yielded a certified steady-state photon-to-electron conversion efficiency of 25.2% and durable stability.

Inhibition of Ion Migration for Highly Efficient and Stable Perovskite Solar Cells

In recent years, organic-inorganic halide perovskites are now emerging as the most attractive alternatives for next-generation photovoltaic devices, due to their excellent optoelectronic characteristics and low manufacturing cost. However, the resultant perovskite solar cells (PVSCs) are intrinsically unstable owing to ion migration, which severely impedes performance enhancement, even with device encapsulation. There is no doubt that the investigation of ion migration and the summarization of recent advances in inhibition strategies are necessary to develop "state-of-the-art" PVSCs with high intrinsic stability for accelerated commercialization. This review systematically elaborates on the generation and fundamental mechanisms of ion migration in PVSCs, the impact of ion migration on hysteresis, phase segregation, and operational stability, and the characterizations for ion migration in PVSCs. Then, many related works on the strategies for inhibiting ion migration toward highly efficient and stable PVSCs are summarized. Finally, the perspectives on the current obstacles and prospective strategies for inhibition of ion migration in PVSCs to boost operational stability and meet all of the requirements for commercialization success are summarized.

Bimolecularly passivated interface enables efficient and stable inverted perovskite solar cells

Compared with the n-i-p structure, inverted (p-i-n) perovskite solar cells (PSCs) promise increased operating stability, but these photovoltaic cells often exhibit lower power conversion efficiencies (PCEs) because of nonradiative recombination losses, particularly at the perovskite/C60 interface. We passivated surface defects and enabled reflection of minority carriers from the interface into the bulk using two types of functional molecules. We used sulfur-modified methylthio molecules to passivate surface defects and suppress recombination through strong coordination and hydrogen bonding, along with diammonium molecules to repel minority carriers and reduce contact-induced interface recombination achieved through field-effect passivation. This approach led to a fivefold longer carrier lifetime and one-third the photoluminescence quantum yield loss and enabled a certified quasi-steady-state PCE of 25.1% for inverted PSCs with stable operation at 65°C for >2000 hours in ambient air. We also fabricated monolithic all-perovskite tandem solar cells with 28.1% PCE.

Utilizing Machine Learning and Diode Physics to Investigate the Effects of Stoichiometry on Photovoltaic Performance in Sequentially Processed Perovskite Solar Cells

Organic-inorganic metal halide perovskite solar cells are renowned for their extensive solution processability, although the production of uniformly crystalline perovskite films can necessitate intricate deposition methods. In our study, we harmonized Shockley diode-based numerical analysis with machine learning techniques to extract the device characteristics of perovskite solar cells and optimize their photovoltaic performance in light of the experimental variables. The application of the Shockley diode equation facilitated the extraction of photovoltaic parameters and the prediction of power conversion efficiencies, thus aiding the understanding of device physics and charge recombination. Through machine learning, specifically Gaussian process regression, we trained models on current-voltage curves sensitive to variations in fabrication conditions, thereby pinpointing the optimal settings for enhanced device performance. Our multifaceted approach not only clarifies the interplay between experimental conditions and device performance but also streamlines the optimization process, diminishing the need for exhaustive trial-and-error experiments. This methodology holds substantial promise for advancing the development and fine-tuning of next-generation perovskite solar cells.

Achieving High Fill Factor in Efficient P-i-N Perovskite Solar Cells

Lead halide perovskite solar cells (PSCs) have made unprecedented progress, exhibiting great potential for commercialization. Among them, inverted p-i-n PSCs provide outstanding compatibility with flexible substrates, more importantly, with silicon (Si) bottom devices for higher efficiency perovskite-Si tandem solar cells. However, even with recently obtained efficiency over 25%, the investigation of inverted p-i-n PSCs is still behind the n-i-p counterpart so far. Recent progress has demonstrated that the fill factor (FF) in inverted PSCs currently still underperforms relative to open-circuit voltage and short-circuit current density, which requires an in-depth understanding of the mechanism and further research. In this review article, the recent advancements in high FF inverted PSCs by adopting the approaches of interfacial optimization, precursor engineering as well as fabrication techniques to minimize undesirable recombination are summarized. Insufficient carrier extraction and transport efficiency are found to be the main factors that hinder the current FF of inverted PSCs. In addition, insights into the main factors limiting FF and strategies for minimizing series resistance in inverted PSCs are presented. The continuous efforts dedicated to the FF of high-performance inverted devices may pave the way toward commercial applications of PSCs in the near future.

Stable and High-Efficiency Perovskite Solar Cells Using Effective Additive Ytterbium Fluoride

With better light utilization, larger tolerance factor, and higher power conversion efficiency (PCE), the HC(NH2 )2 + (FA)-based perovskite is proven superior to the popular CH3 NH3 + (MA)- and Cs-based halide perovskites in solar cell applications. Unfortunately, limited by intrinsic defects within the FA-based perovskite films, the perovskite films can be easily transformed into a yellow δ-phase at room temperature in the fabrication process, a troublesome challenge for its further development. Here, ytterbium fluoride (YbF3 ) is introduced into the perovskite precursor for three objectives. First of all, the partial substitution of Yb3+ for Pb2+ in the perovskite lattice increases the tolerance factor of the perovskite lattice and facilitates the formation of the α phase. Second, YbF3 and DMSO in the solvent form a Lewis acid complex YbF3 ·DMSO, which can passivate the perovskite film, reduce defects, and improve device stability. Consequently, the YbF3 modified Perovskite solar cell exhibits a champion conversion efficiency of 24.53% and still maintains 90% of its initial efficiency after 60 days of air exposure under 30% relative humidity.

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.

Manipulation of Shallow-Trap States in Halide Double Perovskite Enables Real-Time Radiation Dosimetry

Storage phosphors displaying defect emissions are indispensable in technologically advanced radiation dosimeters. The current dosimeter is limited to the passive detection mode, where ionizing radiation-induced deep-trap defects must be activated by external stimulation such as light or heat. Herein, we designed a new type of shallow-trap storage phosphor by controlling the dopant amounts of Ag+ and Bi3+ in the host lattice of Cs2NaInCl6. A distinct phenomenon of X-ray-induced emission (XIE) is observed for the first time in an intrinsically nonemissive perovskite. The intensity of XIE exhibits a quantitative relationship with the accumulated dose, enabling a real-time radiation dosimeter. Thermoluminescence and in situ X-ray photoelectron spectroscopy verify that the emission originates from the radiative recombination of electrons and holes associated with X-ray-induced traps. Theoretical calculations reveal the evolution process of Cl-Cl dimers serving as hole trap states. Analysis of temperature-dependent radioluminescence spectra provides evidence that the intrinsic electron-phonon interaction in 0.005 Ag+@ Cs2NaInCl6 is significantly reduced under X-ray irradiation. Moreover, 0.025 Bi3+@ Cs2NaInCl6 shows an elevated sensitivity to the accumulated dose with a broad response range from 0.08 to 45.05 Gy. This work discloses defect manipulation in halide double perovskites, giving rise to distinct shallow-trap storage phosphors that bridge traditional deep-trap storage phosphors and scintillators and enabling a brand-new type of material for real-time radiation dosimetry.

Tailoring passivators for highly efficient and stable perovskite solar cells

There is an ongoing global effort to advance emerging perovskite solar cells (PSCs), and many of these endeavours are focused on developing new compositions, processing methods and passivation strategies. In particular, the use of passivators to reduce the defects in perovskite materials has been demonstrated to be an effective approach for enhancing the photovoltaic performance and long-term stability of PSCs. Organic passivators have received increasing attention since the late 2010s as their structures and properties can readily be modified. First, this Review discusses the main types of defect in perovskite materials and reviews their properties. We examine the deleterious impact of defects on device efficiency and stability and highlight how defects facilitate extrinsic degradation pathways. Second, the proven use of different passivator designs to mitigate these negative effects is discussed, and possible defect passivation mechanisms are presented. Finally, we propose four specific directions for future research, which, in our opinion, will be crucial for unlocking the full potential of PSCs using the concept of defect passivation.

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.

Engineering ligand reactivity enables high-temperature operation of stable perovskite solar cells

Perovskite solar cells (PSCs) consisting of interfacial two- and three-dimensional heterostructures that incorporate ammonium ligand intercalation have enabled rapid progress toward the goal of uniting performance with stability. However, as the field continues to seek ever-higher durability, additional tools that avoid progressive ligand intercalation are needed to minimize degradation at high temperatures. We used ammonium ligands that are nonreactive with the bulk of perovskites and investigated a library that varies ligand molecular structure systematically. We found that fluorinated aniliniums offer interfacial passivation and simultaneously minimize reactivity with perovskites. Using this approach, we report a certified quasi-steady-state power-conversion efficiency of 24.09% for inverted-structure PSCs. In an encapsulated device operating at 85°C and 50% relative humidity, we document a 1560-hour T₈₅ at maximum power point under 1-sun illumination.

Lead-chelating hole-transport layers for efficient and stable perovskite minimodules

The defective bottom interfaces of perovskites and hole-transport layers (HTLs) limit the performance of p-i-n structure perovskite solar cells. We report that the addition of lead chelation molecules into HTLs can strongly interact with lead(II) ion (Pb²⁺), resulting in a reduced amorphous region in perovskites near HTLs and a passivated perovskite bottom surface. The minimodule with an aperture area of 26.9 square centimeters has a power conversion efficiency (PCE) of 21.8% (stabilized at 21.1%) that is certified by the National Renewable Energy Laboratory (NREL), which corresponds to a minimal small-cell efficiency of 24.6% (stabilized 24.1%) throughout the module area. Small-area cells and large-area minimodules with lead chelation molecules in HTLs had a light soaking stability of 3010 and 2130 hours, respectively, at an efficiency loss of 10% from the initial value under 1-sun illumination and open-circuit voltage conditions.

Lead immobilization for environmentally sustainable perovskite solar cells

Lead halide perovskites are promising semiconducting materials for solar energy harvesting. However, the presence of heavy-metal lead ions is problematic when considering potential harmful leakage into the environment from broken cells and also from a public acceptance point of view. Moreover, strict legislation on the use of lead around the world has driven innovation in the development of strategies for recycling end-of-life products by means of environmentally friendly and cost-effective routes. Lead immobilization is a strategy to transform water-soluble lead ions into insoluble, nonbioavailable and nontransportable forms over large pH and temperature ranges and to suppress lead leakage if the devices are damaged. An ideal methodology should ensure sufficient lead-chelating capability without substantially influencing the device performance, production cost and recycling. Here we analyse chemical approaches to immobilize Pb2+ from perovskite solar cells, such as grain isolation, lead complexation, structure integration and adsorption of leaked lead, based on their feasibility to suppress lead leakage to a minimal level. We highlight the need for a standard lead-leakage test and related mathematical model to be established for the reliable evaluation of the potential environmental risk of perovskite optoelectronics.

Neglected acidity pitfall: boric acid-anchoring hole-selective contact for perovskite solar cells

The spontaneous formation of self-assembly monolayer (SAM) on various substrates represents an effective strategy for interfacial engineering of optoelectronic devices. Hole-selective SAM is becoming popular among high-performance inverted perovskite solar cells (PSCs), but the presence of strong acidic anchors (such as -PO3H2) in state-of-the-art SAM is detrimental to device stability. Herein, we report for the first time that acidity-weakened boric acid can function as an alternative anchor to construct efficient SAM-based hole-selective contact (HSC) for PSCs. Theoretical calculations reveal that boric acid spontaneously chemisorbs onto indium tin oxide (ITO) surface with oxygen vacancies facilitating the adsorption progress. Spectroscopy and electrical measurements indicate that boric acid anchor significantly mitigates ITO corrosion. The excess boric acid containing molecules improves perovskite deposition and results in a coherent and well-passivated bottom interface, which boosts the fill factor (FF) performance for a variety of perovskite compositions. The optimal boric acid-anchoring HSC (MTPA-BA) can achieve power conversion efficiency close to 23% with a high FF of 85.2%. More importantly, the devices show improved stability: 90% of their initial efficiency is retained after 2400 h of storage (ISOS-D-1) or 400 h of operation (ISOS-L-1), which are 5-fold higher than those of phosphonic acid SAM-based devices. Acidity-weakened boric acid SAMs, which are friendly to ITO, exhibits well the great potential to improve the stability of the interface as well as the device.

Minimizing buried interfacial defects for efficient inverted perovskite solar cells

Controlling the perovskite morphology and defects at the buried perovskite-substrate interface is challenging for inverted perovskite solar cells. In this work, we report an amphiphilic molecular hole transporter, (2-(4-(bis(4-methoxyphenyl)amino)phenyl)-1-cyanovinyl)phosphonic acid, that features a multifunctional cyanovinyl phosphonic acid group and forms a superwetting underlayer for perovskite deposition, which enables high-quality perovskite films with minimized defects at the buried interface. The resulting perovskite film has a photoluminescence quantum yield of 17% and a Shockley-Read-Hall lifetime of nearly 7 microseconds and achieved a certified power conversion efficiency (PCE) of 25.4% with an open-circuit voltage of 1.21 volts and a fill factor of 84.7%. In addition, 1-square centimeter cells and 10-square centimeter minimodules show PCEs of 23.4 and 22.0%, respectively. Encapsulated modules exhibited high stability under both operational and damp heat test conditions.

Room temperature nondestructive encapsulation via self-crosslinked fluorosilicone polymer enables damp heat-stable sustainable perovskite solar cells

Encapsulation engineering is an effective strategy to improve the stability of perovskite solar cells. However, current encapsulation materials are not suitable for lead-based devices because of their complex encapsulation processes, poor thermal management, and inefficient lead leakage suppression. In this work, we design a self-crosslinked fluorosilicone polymer gel, achieving nondestructive encapsulation at room temperature. Moreover, the proposed encapsulation strategy effectively promotes heat transfer and mitigates the potential impact of heat accumulation. As a result, the encapsulated devices maintain 98% of the normalized power conversion efficiency after 1000 h in the damp heat test and retain 95% of the normalized efficiency after 220 cycles in the thermal cycling test, satisfying the requirements of the International Electrotechnical Commission 61215 standard. The encapsulated devices also exhibit excellent lead leakage inhibition rates, 99% in the rain test and 98% in the immersion test, owing to excellent glass protection and strong coordination interaction. Our strategy provides a universal and integrated solution for achieving efficient, stable, and sustainable perovskite photovoltaics.

Bulk Perovskite Crystal Properties Determined by Heterogeneous Nucleation and Growth

In metal halide perovskites, charge transport in the bulk of the films is influenced by trapping and release and nonradiative recombination at ionic and crystal defects. Thus, mitigating the formation of defects during the synthesis process of perovskites from precursors is required for better device performance. An in-depth understanding of the nucleation and growth mechanisms of perovskite layers is crucial for the successful solution processing of organic-inorganic perovskite thin films for optoelectronic applications. In particular, heterogeneous nucleation, which occurs at the interface, must be understood in detail, as it has an effect on the bulk properties of perovskites. This review presents a detailed discussion on the controlled nucleation and growth kinetics of interfacial perovskite crystal growth. Heterogeneous nucleation kinetics can be controlled by modifying the perovskite solution and the interfacial properties of perovskites adjacent to the underlaying layer and to the air interface. As factors influencing the nucleation kinetics, the effects of surface energy, interfacial engineering, polymer additives, solution concentration, antisolvents, and temperature are discussed. The importance of the nucleation and crystal growth of single-crystal, nanocrystal, and quasi-two-dimensional perovskites is also discussed with respect to the crystallographic orientation.

Backbone Engineering Enables Highly Efficient Polymer Hole-Transporting Materials for Inverted Perovskite Solar Cells

The interface and crystallinity of perovskite films play a decisive role in determining the device performance, which is significantly influenced by the bottom hole-transporting material (HTM) of inverted perovskite solar cells (PVSCs). Herein, a simple design strategy of polymer HTMs is reported, which can modulate the wettability and promote the anchoring by introducing pyridine units into the polyarylamine backbone, so as to realize efficient and stable inverted PVSCs. The HTM properties can be effectively modified by varying the linkage sites of pyridine units, and 3,5-linked PTAA-P1 particularly demonstrates a more regulated molecular configuration for interacting with perovskites, leading to highly crystalline perovskite films with uniform back contact and reduced defect density. Dopant-free PTAA-P1-based inverted PVSCs have realized remarkable efficiencies of 24.89% (certified value: 24.50%) for small-area (0.08 cm² ) as well as 23.12% for large-area (1 cm² ) devices. Moreover, the unencapsulated device maintains over 93% of its initial efficiency after 800 h of maximum power point tracking under simulated AM 1.5G illumination.

A multiscale ion diffusion framework sheds light on the diffusion-stability-hysteresis nexus in metal halide perovskites

Stability and current-voltage hysteresis stand as major obstacles to the commercialization of metal halide perovskites. Both phenomena have been associated with ion migration, with anecdotal evidence that stable devices yield low hysteresis. However, the underlying mechanisms of the complex stability-hysteresis link remain elusive. Here we present a multiscale diffusion framework that describes vacancy-mediated halide diffusion in polycrystalline metal halide perovskites, differentiating fast grain boundary diffusivity from volume diffusivity that is two to four orders of magnitude slower. Our results reveal an inverse relationship between the activation energies of grain boundary and volume diffusions, such that stable metal halide perovskites exhibiting smaller volume diffusivities are associated with larger grain boundary diffusivities and reduced hysteresis. The elucidation of multiscale halide diffusion in metal halide perovskites reveals complex inner couplings between ion migration in the volume of grains versus grain boundaries, which in turn can predict the stability and hysteresis of metal halide perovskites, providing a clearer path to addressing the outstanding challenges of the field.

Functional Ionic Liquid Polymer Stabilizer for High-Performance Perovskite Photovoltaics

The stability-related issues arising from the perovskite precursor inks, films, device structures and interdependence remain severely under-explored to date. Herein, we designed an ionic-liquid polymer (poly[Se-MI][BF₄ ]), containing functional moieties like carbonyl (C=O), selenium (Se⁺ ), and tetrafluoroborate (BF₄ ^- ) ions, to stabilize the whole device fabrication process. The C=O and Se⁺ can coordinate with lead and iodine (I^- ) ions to stabilize lead polyhalide colloids and the compositions of the perovskite precursor inks for over two months. The Se⁺ anchored on grain boundaries and the defects passivated by BF₄ ^- efficiently suppress the dissociation and migration of I^- in perovskite films. Benefiting from the synergistic effects of poly[Se-MI][BF₄ ], high efficiencies of 25.10 % and 20.85 % were exhibited by a 0.062-cm² device and 15.39-cm² module, respectively. The devices retained over 90 % of their initial efficiency under operation for 2200 h.

The Role of Polymers in Halide Perovskite Resistive Switching Devices

Currently, halide perovskites (HPs) are gaining traction in multiple applications, such as photovoltaics and resistive switching (RS) devices. In RS devices, the high electrical conductivity, tunable bandgap, good stability, and low-cost synthesis and processing make HPs promising as active layers. Additionally, the use of polymers in improving the RS properties of lead (Pb) and Pb-free HP devices was described in several recent reports. Thus, this review explored the in-depth role of polymers in optimizing HP RS devices. In this review, the effect of polymers on the ON/OFF ratio, retention, and endurance properties was successfully investigated. The polymers were discovered to be commonly utilized as passivation layers, charge transfer enhancement, and composite materials. Hence, further HP RS improvement integrated with polymers revealed promising approaches to delivering efficient memory devices. Based on the review, detailed insights into the significance of polymers in producing high-performance RS device technology were effectively understood.

Reducing nonradiative recombination in perovskite solar cells with a porous insulator contact

Inserting an ultrathin low-conductivity interlayer between the absorber and transport layer has emerged as an important strategy for reducing surface recombination in the best perovskite solar cells. However, a challenge with this approach is a trade-off between the open-circuit voltage (V_oc) and the fill factor (FF). Here, we overcame this challenge by introducing a thick (about 100 nanometers) insulator layer with random nanoscale openings. We performed drift-diffusion simulations for cells with this porous insulator contact (PIC) and realized it using a solution process by controlling the growth mode of alumina nanoplates. Leveraging a PIC with an approximately 25% reduced contact area, we achieved an efficiency of up to 25.5% (certified steady-state efficiency 24.7%) in p-i-n devices. The product of V_oc × FF was 87.9% of the Shockley-Queisser limit. The surface recombination velocity at the p-type contact was reduced from 64.2 to 9.2 centimeters per second. The bulk recombination lifetime was increased from 1.2 to 6.0 microseconds because of improvements in the perovskite crystallinity. The improved wettability of the perovskite precursor solution allowed us to demonstrate a 23.3% efficient 1-square-centimeter p-i-n cell. We demonstrate here its broad applicability for different p-type contacts and perovskite compositions.

4-Trifluorophenylammonium Iodide-Based Dual Interfacial Modification Engineering toward Improved Efficiency and Stability of SnO2-Based Perovskite Solar Cells

Passivation engineering has been identified as an effective strategy to eliminate the targeted interfacial defects for improving the efficiency and stability of perovskite solar cells (PSCs). Herein, 4-trifluorophenylammonium iodide (CF₃PhAI) is presented as a multifunctional passivation agent to modify buried SnO₂/perovskite and perovskite/hole transport layer (HTL) interfaces. Upon incorporation of CF₃PhAI between SnO₂ and perovskite, CF₃PhAI can chemically link to SnO₂ via Lewis coordination and electrostatic coupling, thereby effectively passivating under-coordinated Sn and filling the oxygen vacancy. Meanwhile, CF₃PhAI helps anchor PbI₂ and organic cations (MA⁺/FA⁺) to control the crystallization of the perovskite. Consequently, reduced interfacial defects, homogeneous perovskite crystallites, and better energetic alignment can be simultaneously achieved. When CF₃PhAI was further used to modify the perovskite/HTL interface, the fabricated PSCs yielded an impressive power conversion efficiency of 23.06% together with negligible J-V hysteresis. The unencapsulated devices exhibited long-term stability in wet conditions (91.8% efficiency retention after 1000 h) due to the water-resistant CF₃PhAI. We also achieved good light soaking stability, maintaining 86.1% of its initial efficiency after aging for 720 h. Overall, our finding provides a promising strategy for modifying the dual contact interfaces of PSCs toward improved efficiency and stability.

Highly Efficient and Stable Self-Powered Perovskite Photodiode by Cathode-Side Interfacial Passivation with Poly(Methyl Methacrylate)

For several years now, organic-inorganic hybrid perovskite materials have shown remarkable progress in the field of opto-electronic devices. Herein, we introduce a cathode-side passivation layer of poly(methyl methacrylate) (PMMA) for a highly efficient and stable self-powered CH₃NH₃PbI₃ perovskite-based photodiode. For effective noise-current suppression, the PMMA passivation layer was employed between a light-absorbing layer of CH₃NH₃PbI₃ (MAPbI₃) perovskite and an electron transport layer of [6,6]-phenyl-C61-butyric acid methyl ester. Due to its passivation effect on defects in perovskite film, the PMMA passivation layer can effectively suppress interface recombination and reduce the leakage/noise current. Without external bias, the MAPbI₃ photodiode with the PMMA layer demonstrated a significantly high specific detectivity value (~1.07 × 10¹² Jones) compared to that of a conventional MAPbI₃ photodiode without a PMMA layer. Along with the enhanced specific detectivity, a wide linear dynamic response (~127 dB) with rapid rise (~50 μs) and decay (~17 μs) response times was obtained. Furthermore, highly durable dynamic responses of the PMMA-passivated MAPbI₃ photodiode were observed even after a long storage time of 500 h. The results achieved with the cathode-side PMMA-passivated perovskite photodiodes represent a new means by which to realize highly sensitive and stable self-powered photodiodes for use in developing novel opto-electronic devices.

Certified high-efficiency "large-area" perovskite solar module for Fresnel lens-based concentrated photovoltaics

The future of energy generation is well in tune with the critical needs of the global economy, leading to more green innovations and emissions-abatement technologies. Introducing concentrated photovoltaics (CPVs) is one of the most promising technologies owing to its high photo-conversion efficiency. Although most researchers use silicon and cadmium telluride for CPV, we investigate the potential in nascent technologies, such as perovskite solar cell (PSC). This work constitutes a preliminary investigation into a "large-area" PSC module under a Fresnel lens (FL) with a "refractive optical concentrator-silicon-on-glass" base to minimize the PV performance and scalability trade-off concerning the PSCs. The FL-PSC system measured the solar current-voltage characteristics in variable lens-to-cell distances and illuminations. The PSC module temperature was systematically studied using the COMSOL transient heat transfer mechanism. The FL-based technique for "large-area" PSC architectures is a promising technology that further facilitates the potential for commercialization.

Self-powered CH3NH3PbI3 perovskite photodiode with a noise-suppressible passivation layer of poly(methyl methacrylate)

Organohalide perovskite materials and related optoelectronic applications have drawn significant attention due to their promising high-performance photon-to-electricity conversion efficiencies. Herein, we demonstrate a highly sensitive self-powered perovskite-based photodetector created with a noise-current-suppressible passivation layer of poly(methyl methacrylate) (PMMA) at the interface between a CH₃NH₃PbI₃ light-absorbing layer and a NiO_x hole-transporting layer. Along with the defect passivation effect, the PMMA layer effectively diminishes unwanted carrier recombination losses at the interface, resulting in a significant reduction of the leakage/noise current. Consequently, without external bias, a remarkably high level of specific detectivity (∼4.5 × 10¹³ Jones from the dark current and ∼0.81 × 10¹² Jones from the noise current) can be achieved due to the use of the PMMA passivation layer, greatly exceeding those of conventional unpassivated perovskite devices. Moreover, we observed a very wide linear dynamic response range of ∼129 dB together with rapid rise and decay response times of ∼52 and ∼18 µs, respectively. Overall, these results provide a solid foundation for advanced interface-engineering to realize high-performance self-powered perovskite photodetectors for various optoelectronic applications.

Refining Perovskite Heterojunctions for Effective Light-Emitting Solar Cells

Solar cells capable of light-harvesting during daytime and light-emission at night are multifunctional semiconductor devices with many potential applications. Here, it is reported that halide perovskite heterojunction interfaces can be refined to yield stable and efficient solar cells. The cell can also operate effectively as an ultralow-voltage light-emitting diode (LED) with a peak external quantum efficiency of electroluminescence (EQE_EL ) of 3.3%. Spectroscopic and microscopic studies reveal that double-heterojunction refinement with wide-bandgap salts is key to densifying the packing of perovskite grains and enlarging the bandgaps of the perovskite surfaces that are in contact with charge-transport semiconductors. The refined perovskite enables a simple device with dual actions of solar cells and LEDs. This type of all-in-one device has the potential to be used in multifunctional harvesting-storage-utilization (HSU) systems.

Additive engineering with sodium azide material for efficient carbon-based perovskite solar cells

Electron transport layer surface modification approach to enhance overall performance of Carbon electrode based perovskite solar cell.

The current state of the art in internal additive materials and quantum dots for improving efficiency and stability against humidity in perovskite solar cells

The remarkable optoelectronic capabilities of perovskite structures enable the achievement of astonishingly high-power conversion efficiencies on the laboratory scale. However, a critical bottleneck of perovskite solar cells is their sensitivity to the surrounding humid environment affecting drastically their long-term stability. Internal additive materials together with surface passivation, polymer-mixed perovskite, and quantum dots, have been investigated as possible strategies to enhance device stability even in unfavorable conditions. Quantum dots (QDs) in perovskite solar cells enable power conversion efficiencies to approach 20%, making such solar cells competitive to silicon-based ones. This mini-review summarized the role of such QDs in the perovskite layer, hole-transporting layer (HTL), and electron-transporting layer (ETL), demonstrating the continuous improvement of device efficiencies.

High-Performance Perovskite Quantum Dot Solar Cells Enabled by Incorporation with Dimensionally Engineered Organic Semiconductor

Perovskite quantum dots (PQDs) have been considered promising and effective photovoltaic absorber due to their superior optoelectronic properties and inherent material merits combining perovskites and QDs. However, they exhibit low moisture stability at room humidity (20-30%) owing to many surface defect sites generated by inefficient ligand exchange process. These surface traps must be re-passivated to improve both charge transport ability and moisture stability. To address this issue, PQD-organic semiconductor hybrid solar cells with suitable electrical properties and functional groups might dramatically improve the charge extraction and defect passivation. Conventional organic semiconductors are typically low-dimensional (1D and 2D) and prone to excessive self-aggregation, which limits chemical interaction with PQDs. In this work, we designed a new 3D star-shaped semiconducting material (Star-TrCN) to enhance the compatibility with PQDs. The robust bonding with Star-TrCN and PQDs is demonstrated by theoretical modeling and experimental validation. The Star-TrCN-PQD hybrid films show improved cubic-phase stability of CsPbI₃-PQDs via reduced surface trap states and suppressed moisture penetration. As a result, the resultant devices not only achieve remarkable device stability over 1000 h at 20-30% relative humidity, but also boost power conversion efficiency up to 16.0% via forming a cascade energy band structure.

Hole-Transporting Vanadium-Containing Oxide (V2O5-x) Interlayers Enhance Stability of α-FAPbI3-Based Perovskite Solar Cells (∼23%)

Perovskite solar cells (PSCs) have attracted tremendous interest due to their outstanding intrinsic photovoltaic properties, such as absorption coefficients, exciton binding energies, and long carrier lifetimes. Although the power conversion efficiency (PCE) of PSCs is close to the Si solar cells' PCE, device stability remains a challenge. In particular, the device stability is more critical in n-i-p normal structured PSCs, which show a higher efficiency than p-i-n inverted ones, simply because of the much lower stability of 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spi). To prevent the devices from degrading performances arising both from perovskite's degradation and Spi instability, we prepare atomic layer deposition (ALD)-grown transition metal oxides for hole transport with efficient n-i-p PSCs. We demonstrate low-temperature (T_dep = 45 °C)-grown amorphous ALD-V₂O_5-x with oxygen-deficient traps on top of Spi as an interlayer, which prevents the devices' degradation in performance. By blocking moisture and oxygen, ALD-V₂O_5-x was able to greatly improve the devices' stability by preserving the photovoltaic α-FAPbI₃ phase while suppressing both Li ion diffusion from the additive and Au ions from the electrode. As a result, we successfully fabricate PSCs with passivation/hole-transporting bifunctional Spi/ALD-V₂O_5-x interlayers without sacrificing photovoltaic performances, and the device stability is significantly improved.

Enhancing the Efficiency of Perovskite Solar Cells through Interface Engineering with MoS2 Quantum Dots

The interface of perovskite solar cells (PSCs) determines their power conversion efficiency (PCE). Here, the buried bottom surface of a perovskite film is efficiently passivated by using MoS₂ quantum dots. The perovskite films prepared on top of MoS₂-assisted substrates show enhanced crystallinity, as evidenced by improved photoluminescence and a prolonged emission lifetime. MoS₂ quantum dots with a large bandgap of 2.68 eV not only facilitate hole collection but also prevent the photogenerated electrons from flowing to the hole transport layer. Overall promotion leads to decreased trap density and an enhanced built-in electric field, thus increasing the device PCE from 17.87% to 19.95%.