Stability Of Photovoltaic Devices Research Articles

Efficient hole transport layers for silicon heterojunction solar cells by surface plasmonic modification in MoOx/Au NPs/MoOx stacks

This study explores the integration of Au nanoparticles (NPs) into molybdenum oxide (MoOx) thin films to form a MoOx/Au NPs/MoOx (MAM) stack. This stack serves as a hole transport layer (HTL) in silicon heterojunction solar cells, aiming to address the challenges of safety concerns and inefficient carrier transport. Ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy spectra demonstrate that the incorporation of Au NPs notably raises the work function of MAM to 5.85 eV and stabilize Mo6+ concentrations at 94.07%. In addition, Au NPs effectively act as a shield against detrimental interactions with Ag, thereby improving the interfacial stability between the back electrode and HTL. This strategic enhancement facilitates the formation of surface plasmon polaritons, reduces the contact resistance to 41.19 mΩ cm2, and boosts the quantum efficiency by injecting hot electrons and intensifying the surface electric field. These advancements lead to a significant enhancement in the fill factor and short-circuit current, leading to the development of a heterojunction solar cell with an increased efficiency (Eff) from 19.81% to 22.03%. This investigation underscores the transformative potential of engineered nanomaterials in elevating the performance and stability of photovoltaic devices, promoting the wider adoption of renewable energy technologies.

Anomalous Electroluminescence Characteristics of Perovskite Modules.

Spatially resolved photoluminescence (PL) and electroluminescence (EL) imaging technologies play a crucial role in evaluating the performance and stability of photovoltaic devices. However, their application in perovskite devices presents unique challenges. In this study, we report a discrepancy between the electrical performance of perovskite solar modules (PSMs) and the EL images. Following the application of a reverse bias voltage, we observed an increase in EL brightness associated with prolonged carrier lifetime and transport length. Furthermore, cross-sectional Kelvin probe force microscopy identified a significant potential increase primarily at the electron-transport layer (ETL) side after reverse bias, suggesting the presence of defective ETL/perovskite interfaces with filled hole traps. To address this EL mismatch, we proposed a mild reverse current recovery method aimed at aligning EL images with the cell performance without compromising device efficiency. This approach effectively mitigates discrepancies, ensuring alignment between the device performance and EL imaging. Our study underscores that caution is required when utilizing EL imaging to monitor spatial homogeneity in PSMs for future industrial production.

Impact of photoinduced phase segregation in mixed-halide perovskite absorbers on their material and device stability

Mixed-halide perovskites enable bandgap engineering for tandem solar cell and light-emitting diode applications. However, photoinduced halide phase segregation introduces a compositional instability, that is, formation of I-rich and Br-rich phases, which compromises photovoltaic efficiency and stability. While optical and structural studies of the photoinduced phase segregation in mixed-halide perovskites have been reported, its impact on the material stability is missing. Here, a detailed compositional analysis of mixed-halide perovskite films using x-ray and ultraviolet photoelectron spectroscopy (UPS) was carried out to determine how their stability in various environments depends on the halide ratio. A series of perovskite thin films were fabricated with the composition CH3NH3Pb(IxBr1−x)3, where x = 0.00, 0.25, 0.50, 0.75, and 1.00, and analyzed under different conditions, such as exposure to light in ambient and in nitrogen atmosphere, as well as storage in the dark. From the spectroscopy results, complemented with structural and optical properties, it was found that the deletion of halide ions from the surface is facilitated in mixed-halide perovskites in comparison with pure halide perovskites. A higher stability was found for the mixed-halide perovskite containing less than 25% Br, and it decreases with increasing Br content. This study also established the effect of the Br/I ratio on the energy landscape of the materials. The UPS spectra reveal that photoinduced degradation results in a mismatch of the energy levels at the perovskite/transport layer interface, which may limit the collection of charge carriers. These findings correlate well with the photovoltaic device stability under similar degradation conditions.

The Asymmetric Strategy of Small‐Molecule Materials for Organic Solar Cells

AbstractThe conjugated small‐molecule materials of organic solar cells have always played a crucial role in light‐harvesting, charge transport, morphology optimization, and the attainment of efficient devices. The advancement of novel materials and the understanding of underlying molecular design rules serve as the driving force for furthering efficient and stable photovoltaic devices. Among a variety of design principles, the symmetry‐breaking strategy, which is well developed in 3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d’]‐s‐indaceno[1,2‐b:5,6‐b’]dithiophene (ITIC)‐series acceptors, recently demonstrates great potential in small‐molecule acceptors and donors for realizing high power conversion efficiency. In this review, in order to give a deep insight on asymmetric strategy, the small‐molecule acceptors and donors are systematically summarized with asymmetric structure to elucidate structure‐performance relationship, molecular packing behaviors, and morphology evolution. Not only the delicate balance between open circuit voltage and short‐circuit current density, but also the reductions in charge recombination and non‐radiative recombination are considered to play the key points in improving the photovoltaic performance when the asymmetric molecule is used as host or guest materials. Finally, concise challenges and outlooks are provided for the future development and application of asymmetric molecules and symmetry‐breaking strategies.

The dawn of MXene duo: revolutionizing perovskite solar cells with MXenes through computational and experimental methods.

Integrating MXene into perovskite solar cells (PSCs) has heralded a new era of efficient and stable photovoltaic devices owing to their supreme electrical conductivity, excellent carrier mobility, adjustable surface functional groups, excellent transparency and superior mechanical properties. This review provides a comprehensive overview of the experimental and computational techniques employed in the synthesis, characterization, coating techniques and performance optimization of MXene additive in electrodes, hole transport layer (HTL), electron transport layer (ETL) and perovskite photoactive layer of the perovskite solar cells (PSCs). Experimentally, the synthesis of MXene involves various methods, such as selective etching of MAX phases and subsequent delamination. At the same time, characterization techniques encompass X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy, which elucidate the structural and chemical properties of MXene. Experimental strategies for fabricating PSCs involving MXene include interfacial engineering, charge transport enhancement, and stability improvement. On the computational front, density functional theory calculations, drift-diffusion modelling, and finite element analysis are utilized to understand MXene's electronic structure, its interface with perovskite, and the transport mechanisms within the devices. This review serves as a roadmap for researchers to leverage a diverse array of experimental and computational methods in harnessing the potential of MXene for advanced PSCs.

Boosting efficiency above 30 % of novel inorganic Ba3SbI3 perovskite solar cells with potential ZnS electron transport layer (ETL)

The inorganic Ba3SbI3 perovskite has emerged as a promising, stable absorber material for efficient and cost-effective solar cells, owing to its intriguing compositional, structural, electrical, and optical properties. This study delves into the potential of Iodide-based Ba3SbI3 perovskites, known for their relative stability, as absorbers in conjunction with a ZnS electron transport layer (ETL) to create a high-performance solar cell heterostructure. Using the SCAPS-1D simulator, we first estimate the absorption spectrum and bandgap of the Ba3SbI3 absorber layer through density functional theory (DFT). This obtained spectrum serves as a crucial input for device simulation. We further optimize the work function of the rear electrode to enhance the photovoltaic (PV) performance of the ZnS/Ba3SbI3 heterostructure solar cell. Various parameters including doping density, absorber thickness, and bulk/interface defect density are carefully considered. Additionally, we investigated generation and recombination rates, current density-voltage (J-V) characteristics, and corresponding quantum efficiency (QE). Under optimized conditions, our study achieves a remarkable maximum power conversion efficiency (PCE) of 30.49 %, accompanied by a photocurrent density (JSC) of 54.63 mA/cm2, fill factor (FF) of 83.75 %, and open circuit voltage (VOC) of 0.67 V in the ITO/ZnS/Ba3SbI3/Ni structure. This comprehensive analysis offers valuable insights and methodologies for the experimental design of high-performance and stable photovoltaic devices based on Ba3SbI3 perovskite.

Investigating the potential of earth-abundant ZnSnxGe1-xN2 alloys for quantum well solar cells

Zinc Tin Germanium Nitride (ZnSnxGe1-xN2) alloys, which consist of the ternary nitrides ZnSnN2 and ZnGeN2, are notable for being earth-abundant materials that offer numerous advantages over III-V materials in the fields of solar energy conversion and light emission. These benefits include adjustable bandgaps, high absorption coefficients, lower toxicity profiles, and compatibility with silicon-based technology. Developing highly efficient and sustainable photovoltaic (PV) technologies remains crucial in meeting our changing energy needs. In this pursuit, II-IV-V2 compounds and perovskites have recently emerged as promising materials for advancing solar energy conversion. This paper aims to enhance the performance of ZnSnxGe1-xN2/GaN multi-quantum well (MQW) solar cells by conducting thorough simulation and analysis. It explores the effect of different factors, like tin concentration, the number of quantum wells or periods, and operating temperature, on the electrical properties of the PV cell. These characteristics comprise current-voltage (J-V), power-voltage (P–V), and quantum efficiency (QE). Furthermore, vital parameters necessary for all analyses, including strain, critical thickness, absorption coefficients, electric field, and photo-generation rate, have been extensively examined. The research findings presented in this study show that a PV device made up of 50 quantum wells with a tin concentration of 60 % at a temperature of 300K results in considerably improved PV parameters: JSC = 9.23 mA/cm2, VOC = 1.87 V, FF = 73.29 %, and PCE = 12.62 %. These results highlight the significant potential of ZnSnxGe1-xN2/GaN multi-quantum well solar cells as a crucial step towards achieving a more sustainable and efficient energy future. In summary, combining ZnSnxGe1-xN2 alloys with III-N materials presents a promising opportunity to enhance the efficiency and stability of photovoltaic devices. This contributes to the continuous advancement of renewable energy solutions.

The Future of Spirobifluorene‐Based Molecules as Hole‐Transporting Materials for Solar Cells

Organic–inorganic halide perovskite solar cells (PSCs) and organic solar cells (OSCs) attract great attention as alternative renewable photovoltaic technology. The state‐of‐the‐art spiro‐OMeTAD (2,2′,7,7′‐tetrakis‐(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene) is the most successful hole‐transport material (HTM) employed in PSCs, whereas solution‐processed inverted OSCs generally use poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). Recently, various types of spirobifluorene‐based organic small molecules are reported to overcome the known disadvantages of spiro‐OMeTAD, such as the complex synthetic route, high synthetic cost, and requirement for hygroscopic dopants to improve the charge‐carrier mobility and device performance. Examples of spirobifluorene‐based molecules are also reported as alternative HTMs in inverted OSCs to exceed the drawbacks of PEDOT:PSS, such as acidity and batch‐to‐batch reproducibility. These features significantly limit spiro‐OMeTAD and PEDOT:PSS for large‐scale application in the future. Herein, an overview of recent developments in spirobifluorene organic small molecules as HTM in PSCs and OSCs is provided by focusing on synthetic and electrical features. Finally, the further research directions are discussed to develop novel spirobifluorene‐based HTMs for the realization of reliable and long‐term stable photovoltaic devices.

Direct In Situ Conversion of Lead Iodide to a Highly Oriented and Crystallized Perovskite Thin Film via Sequential Deposition for 23.48% Efficient and Stable Photovoltaic Devices.

In the sequential deposition method of perovskite films, the crystallinity and microstructure of PbI2 are often sacrificed to solve the problem of an incomplete reaction between organic halide and lead halide. As a result, the crystal orientation of the perovskite film prepared by the sequential deposition method is generally worse than that of the perovskite film prepared by a one-step antisolvent method. Here, we preplaced formamidine formate (FAFa) on the buried interface to regulate the formation mechanism from PbI2 to perovskite. As shown by the XPS measurement of the perovskite buried interface, the HCOO- anion of FAFa first partially replaces I- to coordinate with Pb2+. With the subsequent annealing process, some HCOO- anions were released and migrated upward, which promoted the recrystallization of PbI2, obtaining a PbI2 film with enhanced crystallinity and orientation. Additionally, the lift-off process proves that the HCOO- anions suppress the anion vacancy defects enriched at the buried interface and promote charge transport because the HCOO- anions are small enough to adapt to the iodide vacancy. Grazing incidence wide-angle X-ray scattering and X-ray diffraction measurements show that the in situ conversion mechanism is responsible for the PbI2-to-perovskite process, resulting in the highly oriented perovskite film without increasing the residual PbI2 content in the perovskite film. As a result, our strategies enabled a champion power conversion efficiency of 23.48% with improved storage stability and photostability. This work provides a new strategy to improve the crystallinity of sequential deposition perovskites without destabilizing the device due to more PbI2 residues.

The modification of ZnO surface with natural antioxidants to fabricate highly efficient and stable inverted organic solar cells

Zinc oxide (ZnO) has proved to be an effective electron transport layer (ETL) in organic solar cells (OSCs). However, a variety of defects on ZnO surface and improperly matched work function (WF) greatly restrict the ability of charge transportationinthe OSCs. Surface modification is an effective strategy for solving these problems. In this work, the ZnO film is modified with three environment-friendly natural antioxidants (NAOs): caffeic acid (CA), ferulic acid (FA) and 3, 4-dimethoxy cinnamic acid (DMCA), respectively. The results show that the modification of NAOs not only effectively passivates the defects of ZnO surface, but also lowers the WF of ZnO by forming interface dipoles and upward shift of Fermi level of ZnO. Moreover, the inverted organic solar cells (IOSCs) with ZnO modified by NAOs as ETLs are firstly fabricated. As the result, the IOSC based on PBDB-T: ITIC obtains the increased PCE of 11.75% (ZnO/CA), 11.25% (ZnO/FA) and 10.90% (ZnO/DMCA), which is higher than those of the reference 10.15% (ZnO). Meanwhile, the PCE of IOSC based on PM6:L8-BO with ZnO/CA ETL is also obviously increased from 16.41% to 18.22%. The ambient stability of the IOSCs new ETLs is also significantly improved due to the increased hydrophobicity of ETL and the enhanced crystallinity of active layer. The novel ETLs provide a facile, eco-friendly, low-cost method to realize the efficient and stable photovoltaic devices.

Controlling Crystallization of Quasi‐2D Perovskite Solar Cells: Incorporating Bulky Conjugated Ligands

AbstractQuasi‐2D hybrid halide perovskites have drawn considerable attention due to their improved stability and facile tunability compared to 3D perovskites. The expansiveness of possibilities has thus far been limited by the difficulty in incorporating large ligands into thin‐film devices. Here, a bulky bi‐thiophene 2T ligand is focused on to develop a solvent system around creating strongly vertically‐aligned (2T)2(MA)6Pb7I22 (n = 7) quasi‐2D perovskite films. By starting with a poorly coordinating solvent (gamma‐butyrolactone) and adding a small amount of dimethylsulfoxide and methanol, it is found that vertical orientation and z‐uniformity is greatly improved. These are carefully examined and verified using grazing‐incidence wide‐angle X‐ray scattering analysis and advanced optical characterizations. These films are incorporated into champion solar cells that achieve a power conversion efficiency of 13.3%, with a short‐circuit current density of 18.9 mA cm‐2, an open‐circuit voltage of 0.96 V, and a fill factor of 73.8%. Furthermore, the quasi‐2D absorbing layers show excellent stability in moisture, remaining unchanged after hundreds of hours. In addition, 2T is compared with the more common ligands butylammonium and phenylethylammonium in this solvent system to develop heuristics and deeper understanding of how to incorporate large ligands into stable photovoltaic devices.

Grain Boundary Defect Controlling of Perovskite via N‐Hydroxysuccinimide Post‐Treatment Process in Efficient and Stable n–i–p Perovskite Solar Cells

Nonradiative recombination on perovskite surface and grain boundary largely constrains the efficiency and stability of photovoltaic devices. Surface passivation has proven to be the most effective strategy to suppress photogenerated carrier recombination. Herein, functional N‐hydroxysuccinimide (NHS) is incorporated in perovskite films by suppressing nonradiative losses both in surface and in grain boundary. The NHS molecules are located at the perovskite grain boundary and surface with good compability with the perovskite crystal network, which forms an effective barrier at the grain boundary to prevent the permeation of moisture. Equally important, the interactions between the CO group in NHS and perovskite undercoordinated groups (Pb2+ or Pb clusters) reduce the surface defects of the perovskite, yielding a minimal energy loss. The prolonged lifetime of carriers with NHS‐treated perovskites prevents the carrier quenching at the perovskite grain boundary and interface. As a result, open‐circuit voltage of the solar cell is up to 1.13 V with a power conversion efficiency (PCE) of 22.21%. The stability of the device is also significantly improved, wherein devices with NHS retain 81% of the initial PCE after 1000 h at room temperature.

Enhancement in the inherent photostability of small molecule-based BHJ device by molecular architecturing

Three small molecules of D-A-D architecture were synthesized with benzothiadiazole as basic acceptor unit. It has been showed previously that the fluorination on the benzothiadiazole acceptor moiety and incorporation of fused thienothiophene spacer have increased the photovoltaic properties [1]. Hence the same strategies have applied here on small molecules to study both the photovoltaic and to tailor the inherent photostability of the material. The first small molecule, TBT (4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole) was designed with benzothiadiazole- acceptor, and thiophene moiety as the donor unit. The effect of fluorine substitution (TDFBT- 5,6-difluoro-4,7-di(thiophen-2-yl) benzo [c][1,2,5]thiadiazole) and incorporation of fused donor moiety (TTBTT- 4,7-bis(thieno[3,2-b] thiophene-2-yl) benzo [c][1,2,5]thiadiazole) on the optical electrochemical, photovoltaic and photostability of the molecules were evaluated. The photostability study on the structurally modified molecules and blend with PCBM shows promising results. Structural modifications of the p-type molecules exhibit an improved photostability of neat films by significantly. The photostability of the active layer comprised of small molecule- PCBM blend has increased by >13.8 times on incorporation of fused thienothiophene (TTBTT) and by a factor of >5.2 on fluorination of acceptor (TDFBT). The results suggest that the structural modification p-type materials not only improve the optical, electrochemical and photovoltaic properties, but also the photostability of BHJ active layer. A careful selection of p-type materials with increased electron affinity with a sensible balancing with ambient stability and band edge matching with that of the n-type material would lead to stable photovoltaic devices.

Solvent evaporation induced preferential crystal orientation BiI3 films for the high efficiency MA3Bi2I9 perovskite solar cells

In this paper, we develop a solvent evaporation induced method and demonstrate that it is effective in suppressing the growth of the BiI 3 (003) crystal plane and favoring the growth of BiI 3 (113) and (300) crystal planes. By using the as-prepared BiI 3 films, we successfully fabricated BiI 3 and MA 3 Bi 2 I 9 (MBI) coexisting films with weakened (006) crystal planes, which are generally oriented parallel to the substrate and prohibit carrier transport. Additionally, compared with MBI films prepared from controlled BiI 3 films, the resultant BiI 3 -MBI film is more suitable for fabricating efficient and stable photovoltaic devices. The best performing photovoltaic device exhibits a power conversion efficiency of 1.53%. This work provides a new strategy for realizing high-efficiency Bi-based perovskite solar cells. The BiI 3 and MBI co-existing films have been successfully fabricated from BiI 3 films with the weakened (003) preferred orientation by the DMF solvent evaporation induced method. The device performance could be improved by regulating the ratio of BiI 3 to MBI in the films. • The preferential crystal orientation of BiI 3 films with (113) and (300) crystal plane was obtained by the DMF solvent evaporation induced method. • The growth of the BiI 3 (003) crystal plane was restricted, which also effectively limited the growth of the MBI (006) crystal plane. • BiI 3 and MBI co-existing perovskite solar cells were fabricated by low pressure vapor assisted solution process.

Cs-content-dependent organic cation exchange in FA1-xCsxPbI3 perovskite

FA-Cs mixed-cation perovskite has been reported as a promising candidate for obtaining highly efficient and stable photovoltaic devices. Phenylethylamine iodide (PEAI) post-treatment is a widely used and effective method for surface passivation of FA-Cs perovskite layer in devices. However, it is still controversial whether the PEAI post-treatment would form two-dimensional (2D) perovskite PEA2PbI4 capping layer or just result in PEA+ terminated surface. Here in this work, the function of PEAI post-treatment on FA-Cs mixed-cation perovskite FA1-xCsxPbI3 (x = 0.1–0.9) with varied Cs contents is elucidated. With increased Cs content, the FA-Cs perovskite shows higher resistance to the cation exchange between FA+ and PEA+. This Cs-content-dependent cation exchange results in the different PEAI reaction preferences with FA-Cs mixed-cation perovskites. Furthermore, higher Cs content with stronger resistance to cation exchange reaction leads to a wider processing window for post-treatment and defect passivation, which is beneficial for the fabrication of large-scale photovoltaic devices.

Multifunctional Heterocyclic-Based Spacer Cation for Efficient and Stable 2D/3D Perovskite Solar Cells.

Two-dimensional/three-dimensional (2D/3D) Ruddlesden-Popper perovskite materials have shown the enormous potential to achieve both efficient and stable photovoltaic devices for commercial applications. Unfortunately, the single function of spacer cations limits their further improvements in efficiency to reach values as high as those of 3D perovskites. Herein, we developed a new-type multifunctional heterocyclic-based spacer cation of 2-(methylthio)-4,5-dihydro-1H-imidazole (MTIm+) to achieve a synchronous improvement of efficiency and stability for 2D/3D perovskite solar cells (PSCs). Owing to the presence of special chemical groups (imidazole and methylthio), strong interactions have been found between MTIm+ and the 3D perovskite component, leading to an excellent passivation effect. More important, at the initial stage of crystallization, uniform nucleation distribution would be generated around the spacer cation, which is helpful for improved crystallinity and reduced growth defects. The smaller layer space compared to that of cations based on aromatic hydrocarbons caused effective carrier transfer between inorganic layers in 2D/3D perovskites. As a result, the 2D/3D (n = 30) PSCs based on MTIm exhibit a champion PCE up to 21.25% with a high Voc of 1.14 V. Besides, the 2D/3D perovskite devices have realized dramatically enhanced humidity and thermal stability, maintaining 94% of the starting PCE enduring aging at about 50% RH for 2880 h and at 85 °C for 360 h, respectively. We believe that it would provide a significant strategy to further promote the photovoltaic performances and the long-term stability of 2D/3D perovskite devices toward future practical applications.

Managing Phase Orientation and Crystallinity of Printed Dion–Jacobson 2D Perovskite Layers via Controlling Crystallization Kinetics

AbstractTwo‐dimensional perovskites have attracted substantial attention for solar cell applications because of their higher stability as compared to their 3D analogs. To achieve efficient charge transport in thin‐film devices, obtaining high crystalline perovskite crystals perpendicularly aligned to the substrate is of great importance. This article reports the scalable printing of high‐quality Dion–Jacobson (DJ) perovskite thin films via tailoring crystallization kinetics. Introducing a small amount of 1‐methyl‐2‐pyrrolidinone to the conventional N,N‐dimethylformamide:dimethyl sulfoxide‐based precursor, the strong coordination with ammonium spacers enables a notably retarded crystallization, which results in perovskite films with distinctly enhanced crystallinity, highly vertical orientation, and graded phase distribution. Accordingly, efficient charge generation and ultrafast interphase charge transfer are realized. The champion DJ perovskite device delivers a high current density of 17.10 mA cm–2, an impressive open‐circuit voltage of 1.21 V, leading to a stabilized efficiency of 16.19%. In addition, the devices processed from the ternary solvent exhibit remarkably improved stability under stimuli with light, heat, and humidity, benefiting from their superb phase stability. This work demonstrates an important advancement in scalable deposition of DJ perovskite thin films for efficient and stable photovoltaic devices.

Multiple‐Ring Aromatic Spacer Cation Tailored Interlayer Interaction for Efficient and Air‐Stable Ruddlesden–Popper Perovskite Solar Cells

2D Ruddlesden–Popper (2DRP) perovskites with hydrophobic bulky cations are proven to improve the environmental stability in photovoltaic devices significantly. However, these spacer cations lead to a weak interplay in the 2DRP perovskites, severely impacting the charge carrier transport and require a systematic understanding of the interaction between spacer cations and inorganic slabs. Herein, a series of novel perovskites (BA1−xNMAx)2MA3Pb4I13 (NMA = 1‐naphthalenemethylammonium, BA = n‐butylammonium) are successfully fabricated to reveal the interaction of mixed spacers and inorganic slabs. Incorporating NMA cations enhances the NH⋯I− hydrogen‐bonding interaction between the spacer cations and [PbI6]4− slabs, resulting in a preferentially crystal vertical orientation of smoothed perovskite films with larger crystal grains. Thus, a significant reduction in the density of trap states of the resulting 2DRP perovskites is achieved which leads to highly efficient charge carrier transport. Consequently, the champion (BA0.9NMA0.1)2MA3Pb4I13 device yields a power conversion efficiency (PCE) of 14.21%, along with the unencapsulated devices that can retain 85% of their initial PCE for 1200 h under 35–65% relative humidity conditions. This work provides a simple and original method to modulate the interlayer interplay in 2DRP perovskites for highly efficient and air‐stable perovskite solar cells.

Solution-processed and annealing-free zirconium acetylacetonate electron-selective contacts for efficient crystalline silicon solar cells

The interfaces between n-type silicon (n-Si) and metal electrode contact have enormous influences on the performance and stability of silicon solar cells. Recently, it has been proven that the carrier-selective contact (CSC) is an effective strategy to improve the device efficiency. Herein, a solution-processed and annealing-free zirconium acetylacetonate (ZrAcac) layer is used as an electron-selective contact for fabricating efficient crystalline silicon solar cell. This contact scheme enabled a reduction in both the contact resistivity and the work function at the interface between n-Si and Al, which can be attributed to the dipole formation at the contact interface induced by charge transfer. The application of this ZrAcac based contact was shown to consistently improve all device parameters reaching a maximum power conversion efficiency of 17.8% with a high fill factor of 81.1%, and greatly improve the device stability. This work demonstrated that the ZrAcac layer can provide sufficient energy alignment and enhanced carrier selectivity for efficient and stable photovoltaic devices.

Low photoactive phase temperature all-inorganic, tin-lead mixed perovskite solar cell.

CsPbI3 films have recently attracted significant attention as efficient absorbers for thermally stable photovoltaic devices. However, their large bandgap and photoactive black phase formation at high temperature impede their use for practical applications. Using the concept of lattice contraction, we demonstrate a low bandgap (≤1.44 eV) cesium-based inorganic perovskite CsPbxSn1−xI3 that can be solution processed at low temperature for photovoltaic devices. The results from systematic measurements imply that the partial substitution of lead (Pb) with tin (Sn) results in crystal lattice contraction, which is essential for realizing photoactive phase formation at l00 °C and stabilizing photoactive phase at room temperature. These findings demonstrate the potential of using cesium-based inorganic perovskite as viable alternatives to MA- or FA-based perovskite photovoltaic materials.