Efficient Air-Processed MA-Free Perovskite Solar Cells by SH-Based Silane Interface Modification.

Air-processed perovskite solar cells (PSCs) with high photoelectric conversion efficiency (PCE) can not only further reduce the production cost but also promote its industrialization. During the preparation of the PSCs in ambient air, the contact of the buried interface not only affects the crystallization of the perovskite film but also affects the interface carrier transport, which is directly related to the performance of the device. Here, we optimize the buried interface by introducing 3-mercaptopropyltrimethoxysilane (MPTMS, (CH3O)3Si(CH2)3SH) on the nickel oxide (NiOx) surface. The crystallization of the perovskite film is improved by enhancing surface hydrophobicity; besides, the SH-based functional group of MPTMS passivates the uncoordinated lead at the interface, which effectively reduces the defects at the bottom interface of perovskite and inhibits the nonradiative recombination at the interface. Moreover, the energy level between the NiOx layer and the perovskite layer is better matched. Based on multiple functions of MPTMS modification, the open circuit voltage of the device is obviously improved, and efficient air-processed methylamine-free (MA-free) PSCs are realized with PCE reaching 21.0%. The device still maintains the initial PCE of 85% after 1000 h aging in the glovebox. This work highlights interface modification in air-processed MA-free PSCs to promote the industrialization of PSCs.

Unveiling Local Current Behavior and Manipulating Grain Homogenization of Perovskite Films for Efficient Solar Cells.

Achieving high power conversion efficiency in perovskite solar cells (PSCs) heavily relies on fabricating homogeneous perovskite films. However, understanding microscopic-scale properties such as current generation and open-circuit voltage within perovskite crystals has been challenging due to difficulties in quantifying intragrain behavior. In this study, the local current intensity within state-of-the-art perovskite films mapped by conductive atomic force microscopy reveals a distinct heterogeneity, which exhibits a strong anticorrelation to the external biases. Particularly under different external bias polarities, specific regions in the current mapping show contrasting conductivity. Moreover, grains oriented differently exhibit varied surface potentials and currents, leading us to associate this local current heterogeneity with the grain orientation. It was found that the films treated with isopropanol exhibit ordered grain orientation, demonstrating minimized lattice heterogeneity, fewer microstructure defects, and reduced electronic disorder. Importantly, devices exhibiting an ordered orientation showcase elevated macroscopic optoelectronic properties and boosted device performance. These observations underscore the critical importance of fine-tuning the grain homogenization of perovskite films, offering a promising avenue for further enhancing the efficiency of PSCs.

Reductive Sn2+ Compensator for Efficient and Stable Sn-Pb Mixed Perovskite Solar Cells.

Tin-lead (Sn-Pb) mixed perovskite with a narrow bandgap is an ideal candidate for single-junction solar cells approaching the Shockley-Queisser limit. However, due to the easy oxidation of Sn2+, the efficiency and stability of Sn-Pb mixed perovskite solar cells (PSCs) still lag far behind that of Pb-based solar cells. Herein, highly efficient and stable FA0.5MA0.5Pb0.5Sn0.5I0.47Br0.03 compositional PSCs are achieved by introducing an appropriate amount of multifunctional Tin (II) oxalate (SnC2O4). SnC2O4 with compensative Sn2+ and reductive oxalate group C2O4 2- effectively passivates the cation and anion defects simultaneously, thereby leading to more n-type perovskite films. Benefitting from the energy level alignment and the suppression of bulk nonradiative recombination, the Sn-Pb mixed perovskite solar cell treated with SnC2O4 achieves a power conversion efficiency of 21.43%. More importantly, chemically reductive C2O4 2- effectively suppresses the notorious oxidation of Sn2+, leading to significant enhancement in stability. Particularly, it dramatically improves light stability.

Polymer Lewis Base for Improving the Charge Transfer in Tin-Lead Mixed Perovskite Solar Cells.

The poor film stability of Sn-Pb mixed perovskite film and the mismatched interface energy levels pose significant challenges in enhancing the efficiency of tin-lead (Sn-Pb) mixed perovskite solar cells. In this study, polyvinylpyrrolidone (PVP) is introduced into the PVK perovskite precursor solution, effectively enhancing the overall stability of the film. This improvement is achieved through the formation of robust coordination bonds between the carbonyl (C=O) in the pyrrole ring and the undercoordinated SnII and PbII, thereby facilitating the passivation of defects. Furthermore, the introduction of PVP inhibits the oxidation of tin (Sn), thereby enhancing the n-type characteristics of the perovskite film. This adjustment in the energy level of the PVK perovskite film proves instrumental in reducing interface energy loss, subsequently improving interface charge transfer and mitigating device recombination. Consequently, perovskite solar cells incorporating PVP achieve an outstanding champion power conversion efficiency (PCE) of 21.31%.

Multifunctional dual-interface layer enables efficient and stable inverted perovskite solar cells.

Considering that the hydrophobicity of PTAA as the surface of an inverted perovskite solar cell (PSC) substrate directly influences the crystallization and top surface properties of perovskite films, dual-interface engineering is a significant strategy to obtain excellent PSCs. PFN-Br was inserted into the PTAA/perovskite interface to ensure close interfacial contact and achieve exceptional crystallization, and then the perovskite top surface was covered with 3-PyAI to further improve its interface property. The mechanism of interaction of PFN-Br and 3-PyAI with perovskites was analyzed through various characterization methods. The results showed that the introduction of a hydrophilic interface layer reduces voids and defects at the bottom of the film. Additionally, the existence of 3-PyAI reduces surface defects, optimizes energy level alignment, and decreases non-radiative recombination, which is beneficial for charge transfer. Consequently, the open circuit voltage (VOC) and fill factor (FF) of the optimized device were greatly enhanced, and the champion device showed a power conversion efficiency (PCE) of 22.07%. The unencapsulated device with PFN-Br&3-PyAI can retain 80% of its initial performance after aging in the air atmosphere (25 °C at a relative humidity (RH) of 25%) for 27 days. Moreover, the reverse bias stability of the device was improved, with the reverse breakdown voltage (VRB) reaching -2 V. This work recommends a dual-interface strategy for efficient and reliable PTAA-based PSCs.

Transcriptome and proteomics conjoint analysis reveal anti-alcoholic liver injury effect of Dianhong Black Tea volatile substances.

Dianhong Black Tea, a fermented tea containing various bioactive ingredients, has been found to have a significant role in alleviating alcoholic liver injury (ALI). One of its main unique components, Dianhong Black Tea volatile substances (DBTVS), may have potential anti-ALI effects. However, its effects and underlying molecular mechanisms are still unknown. In this study, we aimed to investigate the potential of DBTVS as an anti-ALI agent using alcohol-fed rats. We assessed the effect of DBTVS on ALI by analyzing serum transaminase and lipid levels, as well as conducting hematoxylin-eosin and oil red O staining. Additionally, GC-MS was used to detect the components of DBTVS, while transcriptome, proteomics analysis, Western blot, and molecular docking were employed to uncover the underlying mechanisms. Our results demonstrated that DBTVS significantly reduced serum ALT and AST levels and improved lipid metabolism disorders. Moreover, we identified 14 components in DBTVS, with five of them exhibiting strong binding affinity with key proteins. These findings suggested that DBTVS could be a promising agent for the prevention and treatment of ALI. Its potential therapeutic effects may be attributed to its ability to regulate lipid metabolism through the PPAR signaling pathway.

Ternary-Metal Sn-Pb-Zn Perovskite to Reconstruct Top Surface for Efficient and Stable Less-Pb Perovskite Solar Cells.

Though Sn-Pb alloyed perovskite solar cells (PSCs) achieved great progress, there is a dilemma to further increase Sn for less-Pb requirement. High Sn ratio (>70%) perovskite exhibits nonstoichiometric Sn:Pb:I at film surface to aggravate Sn2+ oxidation and interface energy mismatch. Here, ternary metal alloyed (FASnI3 )0.7 (MAPb1- x Znx I3 )0.3 (x = 0-3%) is constructed for Pb% < 30% perovskite. Zn with smaller ionic size and stronger ionic interaction than Sn/Pb assists forming high-quality perovskite film with ZnI6 4- enriched at surface to balance Sn:Pb:I ratio. Differing from uniform bulk doping, surface-rich Zn with lower lying orbits pushes down the energy band of perovskite and adjusts the interface energy for efficient charge transfer. The alloyed PSC realizes efficiency of 19.4% at AM1.5 (one of the highest values reported for Pb% < 30% PSCs). Moreover, stronger bonding of Zn─I and Sn─I contributes to better durability of ternary perovskite than binary perovskite. This work highlights a novel alloy method for efficient and stable less-Pb PSCs.

Identification the Role of Grain Boundaries in Polycrystalline Photovoltaics via Advanced Atomic Force Microscope.

Atomicforce microscopy (AFM)-based scanning probing techniques, including Kelvinprobe force microscopy (KPFM) and conductive atomic force microscopy (C-AFM), have been widely applied to investigate thelocal electromagnetic, physical, or molecular characteristics of functional materials on a microscopic scale. The microscopic inhomogeneities of the electronic properties of polycrystalline photovoltaic materials can be examined by these advanced AFM techniques, which bridge the local properties of materials to overall device performance and guide the optimization of the photovoltaic devices. In this review, the critical roles of local optoelectronic heterogeneities, especially at grain interiors (GIs) and grain boundaries (GBs) of polycrystalline photovoltaic materials, including versatile polycrystalline silicon, inorganic compound materials, and emerging halide perovskites, studied by KPFM and C-AFM, are systematically identified. How the band alignment and electrical properties of GIs and GBs affect the carrier transport behavior are discussed from the respective of photovoltaic research. Further exploiting the potential of such AFM-based techniques upon a summary of their up-to-date applications in polycrystalline photovoltaic materials is beneficial to acomprehensive understanding of the design and manipulation principles of thenovel solar cells and facilitating the development of the next-generation photovoltaics and optoelectronics.

Urea additive improves the performance of low bandgap tin-lead perovskite solar cells.

Recently, narrow bandgap tin-lead mixed perovskite solar cells (PSCs) have become a research hotspot because they can be applied in tandem cells to break the Shockley-Queisser radiative limit of the single junction PSCs. However, the introduction of tin, on the one hand, makes the crystal quality of perovskite thin film worse, leading to the increase of film defects; on the other hand, the easy oxidation of divalent tin also leads to the increase of defect states, which seriously affects the photoelectric conversion efficiency of tin-lead cell devices. Good crystallization and low defect density of perovskite layer are very important to ensure good light absorption and photogenerated carrier generation and transport. Here, we adjust the crystallization of tin-lead perovskite films by a Lewis base-urea (CO(NH2)2), which significantly increases the grain size and improves the film morphology. At the same time, because of the Lewis base property of urea, the uncoordinated Pb2+and Sn2+defects of Lewis acids in the tin-lead films are effectively passivated, and the occurrence of non-radiative recombination in the films is reduced. Under the dual effects of improving crystallization and passivating defects, the photoelectric performance of tin-lead perovskite solar cell devices is significantly improved to 18.1% compared with the original device of 15.4%.

Efficient inverted CsPbI3 inorganic perovskite solar cells achieved by facile surface treatment with ethanolamine.

The all-inorganic CsPbI3 perovskite presents promising prospects due to its suitable band gap and nonvolatile nature, while serious nonradiative recombination and unmatched energy level alignment hinder its further developments. Here, a facile and effective surface treatment strategy is proposed to modify the CsPbI3 surface with ethanolamine, leading to significantly reduced defects, and ameliorated band alignment and morphology. Consequently, a champion power conversion efficiency of 18.41% with improved stability is achieved for the inverted CsPbI3 solar cells.

Advances on the Application of Wide Band-Gap Insulating Materials in Perovskite Solar Cells.

In recent years, the development of perovskite solar cells (PSCs) is advancing rapidly with their recorded photoelectric conversion efficiency reaching 25.8%. However, for the commercialization of PSCs, it is also necessary to solve their stability issue. In order to improve the device performance, various additives and interface modification strategies have been proposed. While, in many cases, they can guarantee a significant increase in efficiency, but not ensure improved stability. Therefore, materials that improve the device efficiency and stability simultaneously are urgently needed. Some wide band-gap insulating materials with stable physical and chemical properties are promising alternative materials. In this review, the application of wide band-gap insulating materials in PSCs, including their preparation methods, working roles, and mechanisms are described, which will promote the commercial application of PSCs.

Influence of the charge transport layers on charge extraction and interface recombination in quasi-two-dimensional perovskite solar cells.

The identification of electronic processes at the charge-selective contact buried interface is very important for photovoltaic research. The main loss of perovskite solar cell (PeSCs) is generally bound up with its charge transfer layer. Especially, the current record for the highest power conversion efficiency of quasi-two-dimensional (quasi-2D) PeSCs is achieved by inverted device configurations, compared with the efficiency of upright structures. This study investigated, the carrier recombination and charge extraction in quasi-2D PeSCs by leveraging scanning probe microscope technology, steady-state photoluminescence (PL) measurements, and time-resolved PL spectroscopy. The built-in potential in quasi-2D bulk perovskite can be regarded as a budget to hinder energy loss in inverted device configurations. Interface photogenerated recombination in quasi-2D PeSCs can be fully comprehended only when the complete device is under consideration. Our work underlines the significance of considering restructuring loss from the perspective of the complete device instead of individual layers or interfaces in quasi-2D PeSCs.

Realizing anti-self-discharged lithium-sulfur batteries by using hierarchical porous carbon nanofibers embedded with Fe/Ni-N catalytic sites.

Lithium-sulfur (Li-S) batteries are featured with high gravimetric energy density, yet their commercial application is significantly deteriorated with the severe self-discharging resulted from the polysulfides shuttle and sluggish electrochemical kinetics. Here, a hierarchical porous carbon nanofibers implanted with Fe/Ni-N (denoted as Fe-Ni-HPCNF) catalytic sites are prepared and used as a kinetics booster toward anti-self-discharged Li-S batteries. In this design, the Fe-Ni-HPCNF possesses interconnected porous skeleton and abundant exposed active sites, enabling fast Li-ion conduction, excellent shuttle inhibition and catalytic ability for polysulfides' conversion. Combined with these advantages, this cell with the Fe-Ni-HPCNF equipped separator exhibits an ultralow self-discharged rate of 4.9% after resting for one week. Moreover, the modified batteries deliver a superior rate performance (783.3 mAh g-1 at 4.0 C) and an outstanding cycling life (over 700 cycles with 0.057% attenuation rate at 1.0 C). This work may guide the advanced design of anti-self-discharged Li-S batteries.

Rational design of formamidine tin-based perovskite solar cell with 30% potential efficiency via 1-D device simulation.

As a promising photovoltaic technology, halide perovskite solar cells (PSCs) have recently attracted wide attention. This work presents a systematic simulation of low bandgap formamidinium tin iodide (FASnI3)-based p-n heterojunction PSCs to investigate the effects of multiple optoelectronic variations on the photovoltaic performance. The structures of the simulated devices are n-i-p, electron transport layer-free (ETL-free), hole transport layer-free (HTL-free), and inverted HTL-free. The simulation is conducted with the Solar Cell Capacitance Simulator (SCAPS-1D). The power conversion efficiencies (PCEs) dramatically decrease when the acceptor doping density (NA) of the absorber layer exceeds 1016 cm-3. For all devices, the photovoltaic parameters dramatically decrease when the absorber defect density (Nt) is over 1015 cm-3, and the best absorber layer thickness is 1000 nm. It should be pointed out that the Nt and the interface defect layer (IDL) are the primary culprits that seriously affect the device performance. When the interfacial defect density (Nit) exceeds 1012 cm-3, PCEs begin to decline significantly. Therefore, paying attention to these defect layers is necessary to improve the PCE. Furthermore, the proper conduction band offset (CBO) between the electron transport layer (ETL) and absorber layer positively affects PSCs' performance. These simulation results help fabricate highly efficient and environment-friendly narrow bandgap PSCs.

Alkali Metal Cations Modulate the Energy Level of SnO2 via Micro-agglomerating and Anchoring for Perovskite Solar Cells.

N-type tin oxide (SnO2) films are commonly used as an electron transport layer (ETL) in perovskite solar cells (PSCs). However, SnO2 films are of poor quality due to facile agglomeration under a low-temperature preparation method. In addition, energy level mismatch between the SnO2 and perovskite (PVK) layer as well as interfacial charge recombination would cause open-circuit voltage loss. In this work, alkali metal oxalates (M-Oxalate, M = Li, Na, and K) are doped into the SnO2 precursor to solve these problems. First, it is found that the hydrolyzed alkali metal cations tend to change colloid size distribution of SnO2, in which Na-Oxalate with suitable basicity leads to most uniform colloid size distribution and high-quality SnO2-Na films. Second, the electron conductivity is enhanced by slightly agglomerated SnO2-Na, which facilitates the transmission of electrons. Third, alkali metal cations increase the conduction band level of SnO2 in the sequence of K+, Na+, and Li+ to promote band alignment between ETLs and perovskite. Based on the optimized film quality and energy states of SnO2-Na, the best PSC efficiency of 20.78% is achieved with a significantly enhanced open-circuit voltage of 1.10 V. This work highlights the function of alkali metal salts on the colloid particle distribution and energy level modulation of SnO2.

Dependence of the Heterogeneity of Grain Boundaries on Adjacent Grains in Perovskites and Its Impact on Photovoltage.

In polycrystalline perovskites, grain boundaries (GBs) that isolate grains determine the optoelectronic properties of a semiconductor, and hence affect the photovoltaic performance of a solar cell. Photocurrent and photovoltage are affected by the microscopic structure of perovskites but are difficult to quantify on the intragrain length scale and are often treated as homogeneous within the photoactive layer. Here, the nanoscale through-film and lateral photoresponse of large-grained perovskite are studied by photoconductive atomic force microscopy. Photocurrent collection along GBs relies on the formation of adjacent grains, exhibiting GB to GB heterogeneity. Regarding to the spatially correlated heterogeneity, the photovoltage of grains deduced from the photoresponse curves at specific positions is larger than that of GBs by up to 0.4 V, suggesting that the photovoltage loss mainly originates from the shunting of GBs through the whole perovskite layer. These spatial heterogeneities are alleviated by depositing a capping layer onto the perovskite layer, highlighting the role of the inserted layer between the perovskite and electrode in real solar cells. This research reveals the heterogeneity of GBs and its influence on photovoltage that actually occurs in virtual solar cells, which is crucial for optimizing perovskite-based solar cells.

Amphiphilic Carborane-Based Covalent Organic Frameworks as Efficient Polysulfide Nano-Trappers for Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) have been considered as one of the most promising energy storage systems because of their high theoretical energy density. However, the "shuttle effect" caused by polysulfide results in poor cycling stability and low electrochemical properties, which strongly impedes the practical application of LSBs. Herein, a kind of amphiphilic carborane-based covalent organic framework (CB-COF) is synthesized and treated as nano-trappers for polysulfide. The microporous CB-COFs show high-temperature resistance and excellent chemical stability. Both experimental results and theoretical calculation indicate the strong adsorption ability of CB-COF for polysulfides. Such an ability makes CB-COF a candidate separator material for LSBs, which efficiently suppresses the "shuttle effect," leading to a high-rate capacity (314 mA h g-1 after 1000 cycles at 2.5 C) and an ultra-long cycling life (after 1000 cycles with a very low decay rate of 0.0395% per cycle at 1 C) of LSBs.

2D-MA3 Sb2 I9 Back Surface Field for Efficient and Stable Perovskite Solar Cells.

In perovskite solar cells (PSCs), a defective perovskite (PVK) surface and cliff-like energy offset at the interface always slow down the charge extraction; meanwhile, interface ion diffusion causes oxidation of the metal electrode, inducing device instability. Here, the in situ grown 2D-(CH3 NH2 )3 Sb2 I9 (MA3 Sb2 I9 ) on the back surface of MAPbI3 results in a more robust interface. MA3 Sb2 I9 changes the MAPbI3 surface to p-type and thus acts like a back surface field to drive charge extraction and suppress recombination, resulting in an obviously higher fill factor (FF) = 0.8 and power conversion efficiency (PCE) = 20.4% of SnO2 /MAPbI3 /MA3 Sb2 I9 /Spiro-OMeTAD (2,2',7,7'-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene) PSC than the pure MAPbI3 device. More importantly, strong chemical bonding of SbI prohibits ion diffusion, largely enhancing the thermal stability and longtime stability. Here, special 2D-MA3 Sb2 I9 constructs' robust band alignment and chemical environment at the interface are highlighted for efficient and stable PSCs.

All in One: A Versatile n-Perovskite/p-Spiro-MeOTAD p-n Heterojunction Diode as a Photovoltaic Cell, Photodetector, and Memristive Photosynapse.

With their excellent optoelectronic properties, halide perovskite (HP) semiconductors have witnessed successful applications in many fields, such as solar cells, LEDs, photodetectors, transistors, and memristors. Exploiting their fascinating physical nature for the development of single nanodevices with multifunctionalities is significant yet remains challenging. We report a multifunctional device based on the n-perovskite/p-spiro-MeOTAD p-n heterojunction diode that enables the integration of photovoltaic, photodetection, and photosynaptic functions in a single device. The device exhibits a high photoelectronic conversion efficiency (PCE) of 17.64% under AM 1.5G illumination and excellent photodetection characteristics including a low drive voltage of 0.01 V, a short response time of 0.17 s, high switching repeatability, and stability. Coupled with the superior photomemristive effect of the device that can be used for the emulation of short- and long-term memory formation of visual synapses, these results suggest that the HP-based p-n heterojunction devices hold great potential in multifunctional integrated device applications.