Dopant-Free Organic Hole-Transporting Material for Efficient and Stable Inverted All-Inorganic and Hybrid Perovskite Solar Cells

Revealing the Role of Spacer Length and Methoxy Substitution of Dipodal Indolocarbazole-based SAMs on the Performance of Inverted Perovskite Solar Cells

The application of self-assembled molecules (SAMs) as selective charge transport layers in inverted perovskite solar cells (iPSCs) has attracted significant interest because of their ability to provide high-efficiency and stable devices. In this work, four dipodal SAMs are reported based on π-expanded indolo[2,3-a]carbazole, incorporated as hole-selective contacts in iPSCs. The presence of methoxy substituents and the spacer length in SAMs are modified to assess their influence on the device performance. For that, the ITO/SAM and ITO/SAM/PSCs interfaces are characterized in detail, including theoretical studies and analysis of the complete device performance. These results demonstrate the multifactorial effect that SAMs have on the growth of crystalline perovskite and the charge dynamics in the devices. The resulting iPSCs show power conversion efficiency (PCE) between 19.76% and 22.20% with fill factors exceeding 82% in all cases and good stability under continuous illumination. Notably, SAM combining unsubstituted indolocarbazole and longer pentyl spacer (5CPICZ) shows the highest PCE of 22.20%. In contrast, analogous SAMs with propyl spacers (3CPICZ) achiev a PCE of 22.01%. The experimental results reveal that the improved PCE reached with unsubstituted indolocarbazole SAMs is attributed to reduced charge recombination and longer carrier lifetime owing to effective perovskite surface passivation.

Innovative Design and Synthesis of Fullerene-Terpyridine Derivatives for Enhanced Electron Transport in Inverted Perovskite Solar Cells

In this study, three fullerene derivatives─C60tBu, C60TPY, and C60TPY-Cl─were synthesized and investigated as additives in PC61BM-based electron-transporting layers (ETLs) for inverted perovskite solar cells (PVSCs). The incorporation of C60tBu and C60TPY into the ETLs led to improved ETL morphology and passivation of crystal defects on the surface of the methylammonium lead iodide (MAPbI3) layer. This defect passivation enhanced crystal quality, increased UV-vis absorption, reduced charge recombination, and improved electron mobility in the C60tBu- and C60TPY-based PVSCs. The passivation effect of C60TPY, which contains a 2,2':6',2″-terpyridine (TPY) unit, was found to be superior to that of C60tBu, which features a t-butyl ester group. As a result, PVSCs utilizing C60TPY exhibited enhanced photovoltaic performance compared to those incorporating C60tBu. To further investigate the contribution of the TPY moiety to the passivation effect, C60TPY was neutralized with HCl to afford C60TPY-Cl. As anticipated, the protonation of the TPY group in C60TPY-Cl resulted in poorer ETL morphology and diminished defect passivation within the MAPbI3 layer. Consequently, no improvement in photovoltaic properties was observed for PVSCs treated with C60TPY-Cl. The architecture of the inverted PVSCs doped with fullerene derivatives consisted of indium tin oxide/NiOx/MAPbI3/fullerene derivative: PC61BM/bathocuproine/Ag. Among the fullerene-based additives, C60TPY demonstrated the highest photovoltaic performance, achieving a power conversion efficiency (PCE) of 20.10%, an open-circuit voltage of 1.07 V, a short-circuit current density of 24.85 mA cm-2, and a fill factor of 75.6%. Furthermore, the C60TPY-based PVSC retained 80% of its initial PCE after 450 h of storage under ambient conditions (30 °C, 40% relative humidity).

Advancements and Strategies in CsPbI2Br Perovskite Solar Cells for Enhanced Efficiency and Stability

In recent years, inorganic perovskite solar cells (IPSCs), especially those based on CsPbI2Br, have attracted considerable attention owing to their exceptional thermal stability and a well-balanced combination of light absorption and phase stability. This review provides an extensive overview of the latest progress in CsPbI2Br PSCs, focusing on film deposition techniques, crystallization control, interface engineering, and charge transport layers (CTLs). High-efficiency CsPbI2Br PSCs can be achieved through the optimization of these key aspects. Various strategies, such as solvent engineering, component/additive engineering, and interface optimization, have been explored to enhance the quality of CsPbI2Br films and improve device performance. Despite significant progress, challenges remain, including the need for even higher quality films, a deeper understanding of interface energetics, and the exploration of novel CTLs. Additionally, long-term stability continues to be a critical concern. Future research should focus on refining film preparation methods, developing sophisticated interfacial layers, exploring compatible charge transport materials, and ensuring device durability through encapsulation and moisture-resistant materials.

Novel quantitative valuation of hybrid perovskite solar cells

As an emerging photovoltaic technology, hybrid perovskite solar cells (PSCs) have achieved excellent performance through rapid development in recent years. High power conversion efficiency (PCE) and excellent stability further promote the commercialization of PSCs. To date, the perovskite light-harvesting active materials are diversified and the device fabrication process is also various. Considered the fabrication costs and steps of PSCs based on different active materials, the quantitative valuation of different hybrid PSCs with PCE above 20% is implemented using data envelopment analysis (DEA) for the first time. This valuation mainly focuses on the inputs (cost and fabrication steps) and outputs (PCE and stability). No weights are needed during the whole analytical process. This ensures the convenience and ease of operation of the analysis, promoting the universality of this method. The results show a detailed analysis of different PSCs from an economic perspective and develop a new way to evaluate PSCs. Meanwhile, the results and this novel valuation method will provide promising guidance for the commercialization of PSCs.

Tuning Isomerism Effect in Organic Bulk Additives Enables Efficient and Stable Perovskite Solar Cells

Organic additives with multiple functional groups have shown great promise in improving the performance and stability of perovskite solar cells. The functional groups can passivate undercoordinated ions to reduce nonradiative recombination losses. However, how these groups synergistically affect the enhancement beyond passivation is still unclear. Specifically, isomeric molecules with different substitution patterns or molecular shapes remain elusive in designing new organic additives. Here, we report two isomeric carbazolyl bisphosphonate additives, 2,7-CzBP and 3,6-CzBP. The isomerism effect on passivation and charge transport process was studied. The two molecules have similar passivation effects through multiple interactions, e.g., P = O···Pb, P = O···H-N and N-H···I. 2,7-CzBP can further bridge the perovskite crystallites to facilitates charge transport. Power conversion efficiencies (PCEs) of 25.88% and 21.04% were achieved for 0.09 cm2 devices and 14 cm2 modules after 2,7-CzBP treatment, respectively. The devices exhibited enhanced operational stability maintaining 95% of initial PCE after 1000 h of continuous maximum power point tracking. This study of isomerism effect hints at the importance of tuning substitution positions and molecular shapes for organic additives, which paves the way for innovation of next-generation multifunctional aromatic additives.

Small-Molecule Hole Transport Materials for >26% Efficient Inverted Perovskite Solar Cells

Chemically modifiable small-molecule hole transport materials (HTMs) hold promise for achieving efficient and scalable perovskite solar cells (PSCs). Compared to emerging self-assembled monolayers, small-molecule HTMs are more reliable in terms of large-area deposition and long-term operational stability. However, current small-molecule HTMs in inverted PSCs lack efficient molecular designs that balance both the charge transport capability and interface compatibility, resulting in a long-standing stagnation of power conversion efficiency (PCE) below 24.5%. Here, we report the comprehensive design of HTMs' backbone and functional groups, which optimizes a simple planar linear molecular backbone with a high mobility exceeding 7.1 × 10-4 cm2 V-1 S-1 and enhances its interface anchoring capability. Owing to the improved surface properties and anchoring effects, the tailored HTMs enhance the interface contact at the HTM/perovskite heterojunction, minimizing nonradiative recombination and transport loss and leading to a high fill factor of 86.1%. Our work has overcome the persistent efficiency bottleneck for small-molecule HTMs, particularly for large-area devices. Consequently, the resultant PSCs exhibit PCEs of 26.1% (25.7% certified) for a 0.068 cm2 device and 24.7% (24.4% certified) for a 1.008 cm2 device, representing the highest PCE for small-molecule HTMs in inverted PSCs.

Structurally Compact Penta(N,N-diphenylamino)corannulene as Dopant-free Hole Transport Materials for Stable and Efficient Perovskite Solar Cells

Hole transport materials (HTMs) are essential for improving the stability and efficiency of perovskite solar cells (PSCs). In this study, we have designed and synthesized a novel organic small molecule HTM, cor-(DPA)5, characterized by a bowl-shaped core with symmetric five diphenylamine groups. Compared to already-known HTMs, the bowl-shaped and relatively compact structure of cor-(DPA)5 facilitates intermolecular π-π interactions, promotes film formations, and enhances charge transport. Consequently, the cor-[DPA(2)]5 HTM exhibits high charge mobility, exceptional hydrophobicity, and a significantly elevated glass transition temperature. Superior to previously reported HTMs such as spiro-OMeTAD and cor-OMePTPA, our newly synthesized cor-(DPA)5 HTM is free from any ionic dopants. As a result, the dopant-free cor-[DPA(2)]5-based PSC demonstrates an impressive efficiency of 24.01 %, and exhibits outstanding operational stability. It retains 96 % after continuous exposure to 1 sun irradiation for 800 hours under MPP (maximum power point) tracking in ambient air. These findings present a structurally compact novel HTM and exemplify a new approach to the molecular design of HTM for the development of stable and effective PSCs.

Development of Dopant-Free N,N'-Bicarbazole-Based Hole Transport Materials for Efficient Perovskite Solar Cells

Efficient and stable hole-transport material (HTM) is essential for enhancing the efficiency and stability of high-efficiency perovskite solar cells (PSCs). The commonly used HTMs such as spiro-OMeTAD need dopants to produce high efficiency, but those dopants degrade the perovskite film and cause instability. Therefore, the development of dopant-free N,N'-bicarbazole-based HTM is receiving huge attention for preparing stable, cost-effective, and efficient PSCs. Herein, we designed and proposed seven distinct small-molecule-based HTMs (B1-B7), which are synthesized and do not require dopants to fabricate efficient PSCs. To design this new series, we performed synergistic side-chain engineering on the synthetic reference molecule (B) by replacing two methylthio (-SCH3) terminal groups with a thiophene bridge and electron-withdrawing acceptor. The enhanced phase inversion geometry of the proposed molecules resulted in reduced energy gaps and better electrical, optical, and optoelectronic properties. Density functional theory (DFT) and time-dependent DFT simulations have been used to study the precise photo-physical and optoelectronic properties. We also looked into the effects of holes and electrons and the materials' structural and photovoltaic properties, including light harvesting energy, frontier molecular orbital, transition density matrix, density of states, electron density matrix, and natural population analysis. Electron density difference maps identify the interfacial charge transfer from the donor to the acceptor through the bridge, and natural population analysis measures the amount of charge on each portion of the donor, bridge, and acceptor, which most effectively represents the role of the end-capped moieties in facilitating charge transfer. Among these designed molecules, the B6 molecule has the greatest absorbance (λmax of 444.93 nm in dichloromethane solvent) and a substantially shorter optical band gap of 3.93 eV. Furthermore, the charge transfer analysis reveals superior charge transfer with improved intrinsic characteristics. Furthermore, according to the photovoltaic analysis, the designed (B1-B7) HTMs have the potential to provide better fill factor and open-circuit voltages, which will ultimately increase the power conversion efficiency (PCE) of PSCs. Therefore, we recommend these molecules for the next-generation PSCs.

6-Trifluoromethylnicotinamide Bilaterally Anchored All Cations Implementing Efficient and Humidity-Stable Perovskite Solar Cells

For organic-inorganic hybrid perovskite solar cells (PSCs), the volatilization of organic components and the presence of undercoordinated Pb2+ ions are the primary causes of device stability imbalance. These factors also serve as significant determinants that restrict the commercialization scale of PSCs. Here, 6-trifluoromethylnicotinamide (TNA) molecules, featuring amide and trifluoromethyl groups at both ends, were introduced as Lewis additives into the precursor solution of perovskite to anchor all cation defect sites and optimize the crystallization process of perovskite. Theoretical calculations confirmed that the -NH2 and C═O groups within the amide group on one side of the TNA molecule synergistically passivated the undercoordinated Pb2+ ions, whereas the trifluoromethyl group on the other side formed hydrogen bonds with the organic components of perovskite. The scorpion-like bilateral all-cation anchoring ability of TNA molecules was further substantiated through experimental characterization. Upon optimization of the TNA treatment concentration, a perovskite film characterized by large grains and a reduced defect density of states was achieved. The photovoltaic performance of PSCs incorporating TNA exhibited significant enhancement with an increase in efficiency from 22.42% (Control) to 24.15%. Under a harsh high-humidity environment, the comprehensive cation passivation effect of TNA significantly hindered the decomposition and phase transition of perovskite films, thereby ensuring excellent humidity stability for the PSCs.

Toward durable all-inorganic perovskite solar cells: from lead-based to lead-free

Organic-inorganic metal halide perovskite solar cells (PSCs) have attracted extensive attention from the photovoltaic (PV) community due to their fast-growing power conversion efficiency from 3.8% to 26.7% in only 15 years. However, these organic-inorganic hybrid PSCs suffer from inferior long-term operational stability under thermal and light stress, due to the fragile hydrogen bonds between organic cations and inorganic slabs. This motivates the exploration of more robust all-inorganic alternatives against external stimuli, by substituting inorganic cesium (Cs) cations for volatile organic cations. Despite reinforced ionic interaction between Cs cations and metal halide frameworks, these Cs-based all-inorganic perovskites tend to undergo spontaneous phase transition from photoactive black phases to non-perovskite yellow phases at room temperature, significantly deteriorating their optoelectronic performance. Thus, tremendous efforts have been made to stabilize the black phase of CsPbI3, while the phase instability issue of the tin-based analogue of CsSnI3 has not been resolved yet. This highlight article summarizes the empirical advances in stabilizing the metastable phases of CsPbI3, aiming to provide useful guidelines to accelerate the development of phase-stable CsSnI3 for durable lead-free PV applications. Finally, the remaining challenges and future research opportunities are outlined, providing a road map to realize efficient and durable all-inorganic perovskite solar cells towards practical applications.

In situ Blending For Co-Deposition of Electron Transport and Perovskite Layers Enables Over 24% Efficiency Stable Conventional Solar Cells

Simplifying the manufacturing processes of multilayered high-performance perovskite solar cells (PSCs) is yet of vital importance for their cost-effective production. Herein, an in situ blending strategy is presented for co-deposition of electron transport layer (ETL) and perovskite absorber by incorporating (3-(7-butyl-1,3,6,8-tetraoxo-3,6,7,8-tetrahydrobenzo- [lmn][3,8]phenanthrolin-2(1H)-yl)propyl)phosphonic acid (NDP) into the perovskite precursor solutions. The phosphonic acid-like anchoring group coupled with its large molecular size drives the migration of NDP toward indium tin oxide (ITO) surface to form a distinct ETL during perovskite film forming. This strategy circumvents the critical wetting issue and simultaneously improves the interfacial charge collection efficiencies. Consequently, n-i-p PSCs based on in situ blended NDP achieve a champion power conversion efficiency (PCE) of 24.01%, which is one of the highest values for PSCs using organic ETLs. This performance is notably higher than that of ETL-free (21.19%) and independently spin-coated (21.42%) counterparts. More encouragingly, the in situ blending strategy dramatically enhances the device stability under harsh conditions by retaining over 90% of initial efficiencies after 250 h in 100 °C or 65% humidity storage. Moreover, this strategy is universally adaptable to various perovskite compositions, device architectures, and electron transport materials (ETMs), showing great potential for applications in diverse optoelectronic devices.

Crystallinity Control and Strain Release in Wide-Bandgap Perovskite Film via Seed-Induced Growth for Efficient Photovoltaics

The seed method stands out as a straightforward and efficient approach for fabricating high-performance perovskite solar cells (PSCs). In this study, we propose the utilization of an antisolvent as an additive to induce crystal seeding, thereby facilitating the growth of wide-bandgap perovskite grains. Specifically, we introduce three commonly used antisolvents─ethyl acetate (EA), isopropanol (IPA), and chlorobenzene (CB)─directly into the perovskite precursor solution to generate perovskite seeds, which serve to promote subsequent nucleation. This antisolvent-crystal seeding method (ACSM) results in increased grain sizes, reduced film defects, and overall improved film quality. Consequently, the power conversion efficiencies (PCEs) of 1.647 eV PSCs with EA, IPA, and CB additives are recorded at 19.86%, 20.61%, and 20.45%, respectively, surpassing that of the reference device with a PCE of 18.83%. Furthermore, the stability of the PSCs prepared through ACSM is notably enhanced. Notably, PSCs optimized with IPA retain 75% of the original PCE after being stored in ambient air conditions (25 °C, RH ∼ 15%) for 30 days, better than the CB-added (64%) and the EA-added devices (53%), while the reference devices only retain 31% of the initial PCE. Moreover, even after continuous thermal annealing at 50 °C for 200 h, IPA-assisted devices demonstrate the best stability, followed by those with CB and EA, with the reference exhibiting the poorest stability.

Room Temperature Ionic Liquid Capping Layer for High Efficiency FAPbI3 Perovskite Solar Cells with Long-Term Stability

Ionic liquid salts (ILs) are generally recognized as additives in perovskite precursor solutions to enhance the efficiency and stability of solar cells. However, the success of ILs incorporation as additives is highly dependent on the precursor formulation and perovskite crystallization process, posing challenges for industrial-scale implementation. In this study, a room-temperature spin-coated IL, n-butylamine acetate (BAAc), is identified as an ideal passivation agent for formamidinium lead iodide (FAPbI3) films. Compared with other passivation methods, the room-temperature BAAc capping layer (BAAc RT) demonstrates more uniform and thorough passivation of surface defects in the FAPbI3 perovskite. Additionally, it provides better energy level alignment for hole extraction. As a result, the champion n-i-p perovskite solar cell with a BAAc capping layer exhibits a power conversion efficiency (PCE) of 24.76%, with an open-circuit voltage (Voc) of 1.19 V, and a Voc loss of ≈330 mV. The PCE of the perovskite mini-module with BAAc RT reaches 20.47%, showcasing the effectiveness and viability of this method for manufacturing large-area perovskite solar cells. Moreover, the BAAc passivation layer also improves the long-term stability of unencapsulated FAPbI3 perovskite solar cells, enabling a T80 lifetime of  3500 h when stored at 35% relative humidity at room temperature in an air atmosphere.

Intermediate Phase Free α-FAPbI3 Perovskite via Green Solvent Assisted Perovskite Single Crystal Redissolution Strategy

Perovskite single-crystal redissolution (PSCR) strategy is highly desired for efficient formamidinium lead triiodide (FAPbI3 ) perovskite photovoltaics with enhanced phase purity, improved film quality, low trap-state density, and good stability. However, the phase transition and crystallization dynamics of FAPbI3 remain unclear in the PSCR process compared to the conventional fabrication from the mixing of precursor materials. In this work, a green-solvent-assisted (GSA) method is employed to synthesize centimeter-sized α-FAPbI3 single crystals, which serve as the high-purity precursor to fabricate perovskite films. The α-FAPbI3 PSCR strategy facilitates direct α-phase formation and inhibits the complex intermediate phases monitored by in situ grazing-incidence wide-angle X-ray scattering. Moreover, the α-phase stability is prolonged due to the relaxation of the residual lattice strain through the isotropic orientation phase growth. Consequently, the GSA-assisted PSCR strategy effectively promotes crystallization and suppresses non-radiative recombination in perovskite solar cells, which boosts the device efficiency from 22.08% to 23.92% with significantly enhanced open circuit voltage. These findings provide deeper insight into the PSCR process in terms of its efficacy in phase formation and lattice strain release. The green low-cost solvent may also offer a new and ideal solvent candidate for large-scale production of perovskite photovoltaics.

Opportunities and challenges of hole transport materials for high-performance inverted hybrid-perovskite solar cells

Inverted perovskite solar cells (inverted-PSCs) have exhibited advantages of longer stability, less hysteresis, and lower fabrication temperature when compared to their regular counterparts, which are important for industry commercialization. Because of the great efforts that have been conducted in the past several years, the obtained efficiency of inverted-PSCs has almost caught up with that of the regular ones, 25.0% versus 25.7%. In this perspective, the recent studies on the design of high-performance inverted-PSCs based on diverse hole transport materials, as well as device fabrication and characterization are first reviewed. After that, the authors moved on to the interface and additive engineering that were exploited to suppress the nonradiative recombination. Finally, the challenges and possible research pathways for facilitating the industrialization of inverted-PSCs were envisaged.

Dynamic self-assembly of small molecules enables the spontaneous fabrication of hole conductors at perovskite/electrode interfaces for over 22% stable inverted perovskite solar cells

The bottom hole transport layers (HTLs) are of paramount importance in determining both the efficiency and stability of inverted perovskite solar cells (PSCs), however, their surface nature and properties strongly interfere with the upper perovskite crystallization kinetics and also influence interfacial carrier dynamics. In this work, we strategically develop a simple, facile and spontaneous fabrication method of the HTL at the perovskite/electrode interface by dynamic self-assembly (DSA) of small molecules during perovskite crystallization. Different from the traditional layer-by-layer approach, this DSA strategy involves a bilateral movement of self-assembled molecules (SAMs) from perovskite solution, realizing simultaneous fabrication of the HTL and perovskite surface passivation. We design a multifunctional molecule, (4-(7H-benzo[c]carbazol-7-yl)butyl)phosphonic acid (BCB-C4PA), for the DSA process, to optimize both self-assembly ability and interfacial energy alignment. Benefitting from this unconventional DSA approach and BCB-C4PA, a champion PCE of 22.2% is achieved along with remarkable long-term environmental stability for over 2750 h, which is among the highest reported efficiencies for SAM-based PSCs. This investigation provides a creative, unique and effective molecular approach for preparing reliable charge transport layers, opening up new avenues for the further development of efficient interfacial contacts for PSCs.

Approaching the Fill Factor Limit in Dopant-Free Hole Transporting Layer-Based All-Inorganic Perovskite Solar Cells

As an important part of perovskite solar cells (PSCs), hole transporting layer (HTL) has a critical impact on the performance and stability of the devices. In an attempt to alleviate the moisture and thermal stability issues from the commonly used HTL Spiro-OMeTAD with dopant, it is urgent to develop novel HTLs with high stability. In this study, a new class of polymers D18 and D18-Cl are applied as undoped HTL for CsPbI₂Br-based PSCs. In addition to the excellent hole transporting properties, we unveil that D18 and D18-Cl with larger thermal expansion coefficient than that of CsPbI₂Br could impose a compressive stress onto the CsPbI₂Br film upon thermal treatment, which could release the residual tensile stress in the film. As a result, the efficiency of CsPbI₂Br-based PSCs with D18-Cl as HTL reaches 16.73%, and the fill factor (FF) exceeds 85%, which is one of the highest FF records for the conventional-structured device to date. The devices also show impressive thermal stability with over 80% of the initial PCE retained after 85 °C heating for 1500 h.

Green-solvent Processable Dopant-free Hole Transporting Materials for Inverted Perovskite Solar Cells

The commercialization of perovskite solar cells (PVSCs) urgently requires the development of green-solvent processable dopant-free hole transporting materials (HTMs). However, strong intermolecular interactions that ensure high hole mobility always compromise the solubility and film-forming ability in green solvents. Herein, we show a simple but effective design strategy to solve this trade-off, that is, constructing star-shaped D-A-D structure. The resulting HTMs (BTP1-2) can be processed by green solvent of 2-methylanisole (2MA), a kind of food additive, and show high hole mobility and multiple defect passivation effects. An impressive efficiency of 24.34 % has been achieved for 2MA-processed BTP1 based inverted PVSCs, the highest value for green-solvent processable HTMs so far. Moreover, it is manifested that the charge separation of D-A type HTMs at the photoinduced excited state can help to passivate the defects of perovskites, indicating a new HTM design insight.

Nexuses Between the Chemical Design and Performance of Small Molecule Dopant-Free Hole Transporting Materials in Perovskite Solar Cells

Perovskite solar cells (PSCs) have grabbed much attention of researchers owing to their quick rise in power conversion efficiency (PCE). However, long-term stability remains a hurdle in commercialization, partly due to the inclusion of necessary hygroscopic dopants in hole transporting materials, enhancing the complexity and total cost. Generally, the efforts in designing dopant-free hole transporting materials (HTMs) are devoted toward small molecule and polymeric HTMs, where small molecule based HTMs (SM-HTMs) are dominant due to their reproducibility, facile synthesis, and low cost. Still, the state-of-art dopant-free SM-HTM has not been achieved yet, mainly because of the knowledge gap between device engineering and molecular designs. From a molecular engineering perspective, this article reviews dopant-free SM-HTMs for PSCs, outlining analyses of chemical structures with promising properties toward achieving effective, low-cost, and scalable materials for devices with higher stability. Finally, an outlook of dopant-free SM-HTMs toward commercial application and insight into the development of long-term stability PSCs devices is provided.

In situ crystal reconstruction strategy-based highly efficient air-processed inorganic CsPbI2Br perovskite photovoltaics for indoor, outdoor, and switching applications

All-inorganic CsPbI₂Br (CPIB) perovskite has gained strong attention due to their favorable optoelectronic properties for photovoltaics. However, solution-processed CPIB films suffer from poor morphology due to the rapid crystallization process, which must be resolved for desirable photovoltaic performance. We introduced phenethylammonium iodide (PEAI) as an additive into a perovskite precursor that effectively controls the crystallization kinetics to construct the preferred quality α-CPIB film under ambient conditions. Various photophysical and structural characterization studies were performed to investigate the microstructural, morphological, and optoelectronic properties of the CPIB and PEAI-assisted perovskite films. We found that PEAI plays a vital role in decreasing pinholes, ensuring precise crystal growth, enhancing the crystallinity, improving the uniformity, and tailoring the film morphology by retarding the crystallization process, resulting in an improved device performance. The device based on the optimized PEAI additive (0.8 mg) achieved a respectably high power conversion efficiency (PCE) of 17.40% compared to the CPIB perovskite solar cell (PSC; 15.75%). Moreover, the CPIB + 0.8 mg PEAI PSC retained ∼87.25% of its original PCE, whereas the CPIB device retained ∼66.90% of the initial PCE after aging in a dry box at constant heating (85 °C) over 720 h, which revealed high thermal stability. Furthermore, the indoor photovoltaic performance under light-emitting diode (LED) lighting conditions (3200 K, 1000 lux) was investigated, and the CPIB + 0.8 mg PEAI PSC showed a promising PCE of 26.73% compared to the CPIB device (19.68%). In addition, we developed a switching function by employing the optimized PSC under LED lighting conditions, demonstrating the practical application of constructed indoor PSCs.

Scanning Electrochemical Microscope Studies of Charge Transfer Kinetics at the Interface of the Perovskite/Hole Transport Layer

Interfacial carrier transfer kinetics is critical to the efficiency and stability of perovskite solar cells. Herein, we measure the regeneration rate constant, absorption cross-section, reduction rate constant, and conductivity of hole transport layered perovskites using scanning electrochemical microscopy (SECM). The SECM feedback revealed that the regeneration rate constant, absorption cross-section, and reduction rate constant of the nickel oxide (NiO) layer perovskite layer are higher than those of the poly (3,4-ethyenedioxythiophene)-poly (styrenesulfonate) layered perovskite. Also, at a specific flux density ( $J_{hv}$ ), the value of the regeneration rate constant (keff) in both blue and red illuminations for the NiO/CH3NH3PbI3 film is significantly higher than in both PEDOT: PSS/CH3NH3PbI3 and FTO/CH3NH3PbI3 films. The difference in keff between layered and nonlayered perovskite conforms to the impact of the hole conducting layer on the charge transfer kinetics. According to the findings, SECM is a powerful approach for screening an appropriate hole transport layer for stable perovskite solar cells.

Underlying Interface Defect Passivation and Charge Transfer Enhancement via Sulfonated Hole-Transporting Materials for Efficient Inverted Perovskite Solar Cells

To date, numbers of polymeric hole-transporting materials (HTMs) have been developed to improve interfacial charge transport to achieve high-performance inverted perovskite solar cells (PSCs). However, molecular design for passivating the underlying surface defects between perovskite and HTMs is a neglected issue, which is a major bottleneck to further enhance the performance of the inverted devices. Herein, we design and synthesize a new polymeric HTM PsTA-mPV with the methylthiol group, in which a lone pair of electrons of sulfur atoms can passivate the underlying interface defects of the perovskite more efficiently by coordinating Pb²⁺ vacancies. Furthermore, PsTA-mPV exhibits a deeper highest occupied molecular orbital (HOMO) level aligned with perovskite due to the π-acceptor capability of sulfur, which improves interfacial charge transfer between perovskite and the HTM layer. Using PsTA-mPV as a dopant-free HTM, the inverted PSCs show 20.2% efficiency and long-term stability, which is ascribed to surface defect passivation, well energy-level matching with perovskite, and efficient charge extraction.

Organic Hole-Transport Layers for Efficient, Stable, and Scalable Inverted Perovskite Solar Cells

Hole-transporting layers (HTLs) are an essential component in inverted, p-i-n perovskite solar cells (PSCs) where they play a decisive role in extraction and transport of holes, surface passivation, perovskite crystallization, device stability, and cost. Currently, the exploration of efficient, stable, highly transparent and low-cost HTLs is of vital importance for propelling p-i-n PSCs toward commercialization. Compared to their inorganic counterparts, organic HTLs offer multiple advantages such as a tunable bandgap and energy level, easy synthesis and purification, solution processability, and overall low cost. Here, recent progress of organic HTLs, including conductive polymers, small molecules, and self-assembled monolayers, as utilized in inverted PSCs is systematically reviewed and summarized. Their molecular structure, hole-transport properties, energy levels, and relevant device properties and resulting performances are presented and analyzed. A summary of design principles and a future outlook toward highly efficient organic HTLs in inverted PSCs is proposed. This review aims to inspire further innovative development of novel organic HTLs for more efficient, stable, and scalable inverted PSCs.

A N-Ethylcarbazole-Terminated Spiro-Type Hole-Transporting Material for Efficient and Stable Perovskite Solar Cells

The development of stable and efficient hole-transporting materials (HTMs) is critical for the commercialization of perovskite solar cells (PSCs). Herein, a novel spiro-type HTM was designed and synthesized where N-ethylcarbazole-terminated groups fully substituted the methoxy group of spiro-OMeTAD, named spiro-carbazole. The developed molecule exhibited a lower highest occupied molecular orbital level, higher hole mobility, and extremely high glass transition temperature (T_g =196 °C) compared with spiro-OMeTAD. PSCs with the developed molecule exhibited a champion power conversion efficiency (PCE) of 22.01 %, which surpassed traditional spiro-OMeTAD (21.12 %). Importantly, the spiro-carbazole-based device had dramatically better thermal, humid, and long-term stability than spiro-OMeTAD.

Self-Powered and Low-Noise Perovskite Photodetector Enabled by a Novel Dopant-Free Hole-Transport Material with Bottom Passivation for Underwater Blue Light Communications

Designing dopant-free hole-transport materials (HTMs) is a facile and effective strategy to realize high-performance organic-inorganic hybrid perovskite (OIHP) photodetectors. Herein, a novel phenothiazine polymer, poly[4-(10H-phenothiazin-10-yl)-N,N-bis(4-methoxyphenyl)aniline] (PPZ-TPA), was synthesized and employed as a promising HTM in OIHP photodetectors. The triphenylamine donor unit was combined with a phenothiazine core, furnishing the polymer with a suitable highest occupied molecular orbital level, favorable thermal stability, and appropriate film morphology. The sulfur atom in the phenothiazine functional group can intentionally passivate the undercoordinated Pb²⁺ of OIHP films, suppressing nonradiative recombination and yielding an ultralow dark current density of 1.26 × 10^-7 A cm^-2 under -0.1 V, as well as a low-noise current of 3.75 × 10^-13 A Hz^-1/2 at 70 Hz. Encouragingly, the self-powered PPZ-TPA-based OIHP photodetectors were successfully integrated into a blue light communication system for the first time, demonstrating their application for receiving and transmitting light signals with a transmission rate of 300 bps. In addition, the PPZ-TPA-based devices exhibit nearly 1 year shelf stability without obvious degradation. We believe that PPZ-TPA demonstrates great potential to achieve high-performance perovskite photodetectors, also providing a strategy for the design of novel HTMs.

Molecular Engineering of Peripheral Substitutions to Construct Efficient Acridine Core-Based Hole Transport Materials for Perovskite Solar Cells

The development of highly efficient hole transport materials (HTMs) for perovskite solar cells (PSCs) has been a hot research topic. Acridine and its derivatives are gradually utilized as new blocks for optoelectronic applications, which stems from its rigid conjugated structure, shedding a new light on this old molecule. Meanwhile, its application in PSCs as a HTM has not been well explored, and the efficiency of 9,10-dihydroacridine (ACR)-based HTMs is relatively low. In this work, we conduct a systematic modulation of the peripheral substituents for ACR core building block-based HTMs and investigate the effects of the electron-donating ability and π-conjugation of peripheral groups on the photovoltaic performance of the corresponding HTMs. It is found that the peripheral groups with a weaker electron-donating ability and stronger π-conjugation are more suitable for the acridine core, which itself has a stronger electron-donating ability. Through molecular engineering, the newly developed HTM ACR-PhDM achieves an impressive power conversion efficiency of 23.5%. Our work lays the foundation for the design and development of efficient HTMs in the future.

Oxidation of Spiro-OMeTAD in High-Efficiency Perovskite Solar Cells

2,2',7,7'-Tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD), as an organic small molecule material, is the most commonly employed hole transport material (HTM) in perovskite solar cells (PSCs) because of its excellent properties that result in high photovoltaic performances. However, the material still suffers from low conductivity, leading to the necessary use of dopants and oxidative processes to overcome this issue. The spiro-OMeTAD oxidation process is highlighted in this review, and the main parameters involved in the process have been studied. Furthermore, the best alternatives aiming to improve the spiro-OMeTAD electrical properties have been discussed. Lastly, this review concludes with suggestions and outlooks for further research directions.

Synchronous Surface Reconstruction and Defect Passivation for High-Performance Inorganic Perovskite Solar Cells

The nonradiative charge recombination caused by surface defects and inferior crystalline quality are major roadblocks to further enhancing the performance of CsPbI_{3- x} Br_x perovskite solar cells (PSCs). Theoretical calculations indicate that sodium diethyldithiocarbamate (NaDDTC), a popular bacteriostatic benign material, can initiate multiple interactions with the CsPbI_{3- x} Br_x perovskite surface to effectively passivate the defects. The experimental results reveal that the NaDDTC can indeed passivate the electron trap states and lock active sites for charge traps and water adsorption. In addition, it is found that a solid-state reaction is triggered for perovskite crystal regrowth by the NaDDTC post-treatment, which not only enlarges grain size for reducing the density of grain boundary defects but also compensates some surface defects induced by the primary film growth. Consequently, the power conversion efficiency (PCE) of the CsPbI_{3- x} Br_x PSC is increased to as high as 20.40%, with significant improvement in fill factor and open-circuit voltage (V_OC ), making it one of the highest for this type of solar cell. Furthermore, the optimized devices exhibit better environmental stability. Overall, this robust synchronous strategy provides efficient surface reconstruction and defect passivation for achieving both high PCE and stable inorganic perovskite.

A Multifunctional Fluorinated Polymer Enabling Efficient MAPbI3-Based Inverted Perovskite Solar Cells

Exploring polymeric hole-transporting materials (HTMs) with passivation functions represents a simplified and effective approach to minimize the perovskite defect density. To date, most of reported polymeric HTMs were applied to fabricate n-i-p regular perovskite solar cells (PSCs). The polymers compatible for p-i-n inverted PSCs were very limited. Moreover, the passivation polymers were devoted to passivate the uncoordinated Pb²⁺. However, the MA⁺ cation defect has profound unwanted effect on device efficiency and long-term stability. In order to synchronously passivate the Pb²⁺ and MA⁺ defects in p-i-n inverted PSCs, a new nonfused polymer was intentionally explored via mild polymerization. The aromatic bridge instead of long alkyl chains enabled polymer BN-12 to achieve excellent thermal stability and good wettability of perovskite precursor. Furthermore, the incorporation of chemical anchor sites ("C═O" and "F") strongly controlled the crystallization of perovskite and restrained the MA⁺ ion migration. As a result, a significant fill factor (FF) of 82.9% and an enhanced power conversion efficiency (PCE) of 20.28% were achieved for MAPbI₃-based devices with the dopant-free BN-12, exceeding those with the commercial HTM PTAA (FF = 81.7%, PCE = 19.51%). More importantly, the unencapsulated devices based on BN-12 realized outstanding long-term stability, maintaining approximately 95% of its initial efficiency after stored for 85 days. By contrast, the PTAA-based device showed rapid decrease which retained only 50% of its initial value after 45 days.

Controlled Growth and Self-Assembly of Multiscale Organic Semiconductor

Currently, organic semiconductors (OSs) are widely used as active components in practical devices related to energy storage and conversion, optoelectronics, catalysis, and biological sensors, etc. To satisfy the actual requirements of different types of devices, chemical structure design and self-assembly process control have been synergistically performed. The morphology and other basic properties of multiscale OS components are governed on a broad scale from nanometers to macroscopic micrometers. Herein, the up-to-date design strategies for fabricating multiscale OSs are comprehensively reviewed. Related representative works are introduced, applications in practical devices are discussed, and future research directions are presented. Design strategies combining the advances in organic synthetic chemistry and supramolecular assembly technology perform an integral role in the development of a new generation of multiscale OSs.

Triarylamine-Functionalized Imidazolyl-Capped Bithiophene Hole Transporting Material for Cost-Effective Perovskite Solar Cells

Triarylamine end-capped-functionalized arylene-imidazole derivatives were synthesized from readily accessible, inexpensive precursors and employed as hole transporting materials (HTMs) in perovskite solar cells (PSCs). All the HTMs displayed high thermal decomposition temperatures (>410 °C), which is beneficial for realizing stable PSC devices. In addition, the new HTMs show appropriate energy level alignment with the perovskite layer, ensuring efficient hole transfer from perovskites to HTMs. Interestingly, PSCs fabricated with the triarylamine-functionalized imidazolyl-capped bithiophene molecule (DImBT-4D) as the HTM exhibited the best power conversion efficiency of 20.11%, comparable to that of the benchmark HTM spiro-OMeTAD, prompting it be a prospective candidate for large-scale PSC applications.

Evaluating the Capacitive Response in Metal Halide Perovskite Solar Cells

The perovskites solar cells (PSCs) is composed of multifaceted device architecture and involve complex charge extraction (both electronic and ionic), this makes the task demanding to unlock the origin of the different physical process that occurs in a PSC. The capacitance in PSCs depends on several external perturbations including frequency, illumination, temperature, applied bias, and importantly on the interface modification of perovskites/charge selective contact. Arguably, different features including interfacial and bulk; ionic, and electronic charge transport in PSCs occur at different time scales. Capacitance spectroscopy is a prevailing technique to unravel the various physical phenomenon that occurs in a PSC at different time scales. A deeper knowledge of the capacitive response of a PSCs is essential to understand the charge carrier kinetics and unlock the device physics. This work highlights the capacitive response of PSCs and its application to unlock the device physics which is essential for the further optimization and improvement of the device performance.

Interface Regulation by an Ultrathin Wide-Bandgap Halide for Stable and Efficient Inverted Perovskite Solar Cells

The nonradiative recombination between hole transport layers (HTLs) and perovskites generally leads to obvious energy losses. The trap states at the HTL/perovskite interface directly influence the improvement of the power conversion efficiency (PCE) and stability. Interface regulation is a simple and commonly used method to decrease nonradiative recombination in inverted perovskite solar cells (PSCs). Here, a wide-bandgap halide was used to regulate the PTAA/MAPbI₃ interface, in which n-hexyltrimethylammonium bromide (HTAB) was used to modify the upper surface of poly[bis(4-phenyl)-(2,4,6-trimethylphenyl)amine] (PTAA). Upon introduction of the HTAB layer, the contact between PTAA and MAPbI₃ is strengthened, the defect state density in PSCs is reduced, the MAPbI₃ crystallinity is improved, and the nonradiative recombination loss is suppressed. The device with HTAB delivers the highest PCE of 21.01% with negligible hysteresis, which is significantly higher than that of the control device (17.71%), and it maintains approximately 87% of its initial PCE for 1000 h without encapsulation in air with a relative humidity of 25 ± 5%. This work reveals an effective way of using a wide-bandgap halide to regulate the PTAA/MAPbI₃ interface to simultaneously promote the PCE and stability of PSCs.

Resonance-Mediated Dynamic Modulation of Perovskite Crystallization for Efficient and Stable Solar Cells

Manipulating perovskite crystallization to prepare high-quality perovskite films is the key to achieving highly efficient and stable perovskite solar cells (PSCs). Here, a dynamic strategy is proposed to modulate perovskite crystallization using a resonance hole-transporting material (HTM) capable of fast self-adaptive tautomerization between multiple electronic states with neutral and charged resonance forms for mediating perovskite crystal growth and defect passivation in situ. This approach, based on resonance variation with self-adaptive molecular interactions between the HTM and the perovskite, produces high-quality perovskite films with smooth surface, oriented crystallization, and low charge recombination, leading to high-performance inverted PSCs with power conversion efficiencies approaching 22% for small-area devices (0.09 cm² ) and up to 19.5% for large-area devices (1.02 cm² ). Also, remarkably high stability of the PSCs is observed, retaining over 90%, 88%, or 83% of the initial efficiencies in air with relative humidity of 40-50%, under continuous one-sun illumination, or at 75 °C annealing for 1000 h without encapsulation.

A double perovskite participation for promoting stability and performance of Carbon-Based CsPbI2Br perovskite solar cells

All-inorganic perovskite materials (Typically: CsPbI₂Br) have attracted enormous attention due to their illustrious thermal stability and appropriate bandgap, and their use in perovskite solar cells (PSCs) has been extensively investigated. However, the inevitable defects of the perovskite layer, energy level mismatch between perovskite and carbon electrodes, and the phase instability of CsPbI₂Br limit the power conversion efficiency (PCE) and stability of carbon-based CsPbI₂Br PSCs. Herein, we demonstrate a simple and effective strategy for regulating energy level, inhibiting carrier recombination, and delaying the degradation of perovskite by modifying the surface of CsPbI₂Br with a new type of 2D perovskite Cs₂PtI₆. The carbon-based CsPbI₂Br PSCs achieve a higher PCE (13.69 %) than the control device (11.10 %). The excellent matching of the energy level and suppression of charge carrier recombination should be responsible for the improvement in efficiency. Furthermore, the excellent hydrophobic performance of Cs₂PtI₆ enhances the moisture resistance of the device. This study provides a potential strategy for improving the performance and stability of all-inorganic CsPbI₂Br PSCs.

Pressure-Enhanced Vertical Orientation and Compositional Control of Ruddlesden-Popper Perovskites for Efficient and Stable Solar Cells and Self-Powered Photodetectors

It is well-known that two-dimensional Ruddlesden-Popper (2DRP) perovskite has higher stability than three-dimensional counterparts. However, fundamental issues still exist in the vertical orientation and phase composition as well as phase distribution. Here, obvious control of the film quality of 2DRP PEA₂MA₄Pb₅I₁₆ (n = 5) perovskite is demonstrated via a thermal-pressed (TP) effect. The crystallinity, morphology, phase composition, and optoelectronic features unequivocally illustrate that the TP effect achieves a larger gain size, a smoother surface, an effectively vertical orientation, a relatively pure phase with a large n value, a gradient distribution of quantum wells, and enhanced interlayer interaction. These film and interface features lead to markedly enhanced charge transport/extraction and lower trap density. Accordingly, the TP-based perovskite film device delivers a power conversion efficiency of 15.14%, far higher than that of the control film device (11.10%) because of significant improvements in open-circuit voltage and short-circuit current. More importantly, it also presents excellent hydrophobicity, illumination stability, and environmental stability. In addition, the 2D perovskite self-powered photodetector also exhibits high responsivity (0.25 A W^-1) and specific detectivity (1.4 × 10¹² Jones) at zero bias.

Spiro[cyclopentadithiophene-dioxolane]-Based D-A-D Type Organic Molecule for Both Crystallization Improvement and Band Adjustment of Perovskites

To improve the crystallization and meanwhile adjust the band levels of perovskites, we design and synthesize a novel organic molecule, 4,4'-(spiro[cyclopenta[1,2-b:5,4-b']dithiophene-4,2'-[1,3]dioxolane]-2,6-diyl)bis(N,N-bis(4-methoxyphenyl)aniline) (TM1), to dissolve in an antisolvent for the antisolvent engineering of perovskite solar cells (PSCs). The coordination interactions between TM1 and Pb²⁺ ions in perovskites and the hydrogen bonds between the O atoms in the methoxy of TM1 and the MA⁺ in perovskites are characterized with X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Owing to these interactions, TM1 can improve the perovskite crystallization, which reduces the trap density, enhances the interfacial hole extraction, and retards charge recombination as well, boosting short-circuit photocurrent notably. TM1 also shifts the valence band of perovskites upward by 0.17 eV, which aligns better with the highest occupied molecular orbital of hole transport materials and thus increases the open-circuit photovoltage significantly. As a result, the power conversion efficiency is enhanced from 17.22 to 20.21% by TM1. Moreover, TM1 can also improve device stability significantly. These findings demonstrate that TM1 is a kind of functional material as an additive in an antisolvent for both crystallization improvement and energy level adjustment of perovskites toward highly efficient and stable PSCs.

Intramolecular Noncovalent Interaction-Enabled Dopant-Free Hole-Transporting Materials for High-Performance Inverted Perovskite Solar Cells

Intramolecular noncovalent interactions (INIs) have served as a powerful strategy for accessing organic semiconductors with enhanced charge transport properties. Herein, we apply the INI strategy for developing dopant-free hole-transporting materials (HTMs) by constructing two small-molecular HTMs featuring an INI-integrated backbone for high-performance perovskite solar cells (PVSCs). Upon incorporating noncovalent S⋅⋅⋅O interaction into their simple-structured backbones, the resulting HTMs, BTORA and BTORCNA, showed self-planarized backbones, tuned energy levels, enhanced thermal properties, appropriate film morphology, and effective defect passivation. More importantly, the high film crystallinity enables the materials with substantial hole mobilities, thus rendering them as promising dopant-free HTMs. Consequently, the BTORCNA-based inverted PVSCs delivered a power conversion efficiency of 21.10 % with encouraging long-term device stability, outperforming the devices based on BTRA without S⋅⋅⋅O interaction (18.40 %). This work offers a practical approach to designing charge transporting layers with high intrinsic mobilities for high-performance PVSCs.

A Universal Dopant-Free Polymeric Hole-Transporting Material for Efficient and Stable All-Inorganic and Organic-Inorganic Perovskite Solar Cells

Hole-transporting materials (HTMs) with desired properties play a crucial role in achieving efficient and stable perovskite solar cells (PSCs). However, most high-performance devices generally employ HTMs that require additional complicated doping treatments, which are harmful to the device stability. In this work, a fluorine-substituted polymer electron-donor material, PM6, is developed as a dopant-free HTM in regular all-inorganic CsPbI2Br PSCs. Benefiting from the matched energy-level alignment, high hole mobility, and effective defect passivation, a champion power conversion efficiency (PCE) of 16.06% with an ultrahigh fill factor of 82.54% is achieved for the PM6-based PSCs. Compared to doped Spiro-OMeTAD (PCE of 14.46%), PM6 significantly enhances the PCE of CsPbI2Br PSCs with negligible hysteresis owing to its more efficient charge transportation, suppressed recombination, and strong trap passivation effect. Moreover, remarkable improvements in long-term stability, thermal stability, and operational stability are all gained for the PM6-based PSCs. In addition, the successful application of PM6 as a dopant-free HTM in organic-inorganic hybrid PSCs enables an impressive PCE of 20.05% with superb device stability, manifesting the generality of the polymer donor material in various PSC systems.

Interfaces and Interfacial Layers in Inorganic Perovskite Solar Cells

Owing to their superior thermal stability, metal halide inorganic perovskite materials continue to attract interest for photovoltaics applications. The highest reported power conversion efficiency (PCE) for solar cells based on inorganic perovskites is over 20 %. As this PCE corresponds to 73 % of the theoretical limit, there remains more room for further improving the device PCEs than for improving organic-inorganic hybrid perovskite solar cells (PSCs). The main loss is in the photovoltage, which is limited by interfaces in terms of non-radiative recombination caused by traps and energy-level mismatch. Furthermore, inefficient charge extraction at interfacial contacts reduces the photocurrent and fill factor. This Minireview summarizes the recent developments in the fundamental understanding of how the interfaces and interfacial layers influence the performance of solar cells based on inorganic perovskite absorbers. An outlook for the development of highly efficient and stable inorganic PSCs from the interface point of view is also given.

Gold Nanomaterials and Bone/Cartilage Tissue Engineering: Biomedical Applications and Molecular Mechanisms

Recently, as our population increasingly ages with more pressure on bone and cartilage diseases, bone/cartilage tissue engineering (TE) have emerged as a potential alternative therapeutic technique accompanied by the rapid development of materials science and engineering. The key part to fulfill the goal of reconstructing impaired or damaged tissues lies in the rational design and synthesis of therapeutic agents in TE. Gold nanomaterials, especially gold nanoparticles (AuNPs), have shown the fascinating feasibility to treat a wide variety of diseases due to their excellent characteristics such as easy synthesis, controllable size, specific surface plasmon resonance and superior biocompatibility. Therefore, the comprehensive applications of gold nanomaterials in bone and cartilage TE have attracted enormous attention. This review will focus on the biomedical applications and molecular mechanism of gold nanomaterials in bone and cartilage TE. In addition, the types and cellular uptake process of gold nanomaterials are highlighted. Finally, the current challenges and future directions are indicated.

Managing Defects Density and Interfacial Strain via Underlayer Engineering for Inverted CsPbI2 Br Perovskite Solar Cells with All-Layer Dopant-Free

Inorganic perovskite CsPbI₂ Br has advantages of excellent thermal stability and reasonable bandgap, which make it suitable for top layer of tandem solar cells. Nevertheless, solution-processed all-inorganic perovskites generally suffer from high-density defects as well as significant tensile strain near underlayer/perovskite interface, both leading to compromised device efficiency and stability. In this work, the defect density as well as interfacial tensile strain in inverted CsPbI₂ Br perovskite solar cells (PeSCs) is remarkably reduced by using a bilayer underlayer composed of dopant-free 2,2',7,7'-tetrakis(N,N-dip-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD) and copper phthalocyanine 3,4',4″,4'″-tetrasulfonated acid tetrasodium salt (TS-CuPc) nanoparticles. As compared to control devices with pristine Spiro-OMeTAD, devices based on Spiro-OMeTAD/TS-CuPc exhibit remarkably improved photovoltaic performance and enhanced thermal/humidity stability due to the better perovskite crystallization, improved interfacial passivation, and hole-collection as well as efficient interfacial strain release. As a result, a champion efficiency of 14.85% can be achieved, which is approaching to the best reported for dopant-free and inverted all-inorganic PeSCs. The work thus provides an efficient strategy to simultaneously regulate the defects density and strain issue related to inorganic perovskites.