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Improving performance and stability of planar perovskite solar cells through grain boundary passivation with block copolymer
摘要： Organic-inorganic metal halide perovskite solar cells (PSCs) exhibit excellent photovoltaic performance but suffer from instabilities against moisture and heat due to the inherent hydroscopic nature and volatility of their organic components. Herein, we report that employing block copolymer F127 as the passivation reagent in conjunction with solvent annealing process can efficiently improve the performance and stability of corresponding organic-inorganic PSCs. It is anticipated that the hydrophilic poly(ethylene oxide) tails of F127 polymers connect with contiguous perovskite crystals and passivate defects at perovskite grain boundaries, whereas the dangling hydrophobic poly(phenyl oxide) centers suppress perovskite decomposition caused by moisture and heat. After the optimization of the F127 additive, the planar PSCs with champion power conversion efficiencies of 21.01% and 18.71% were achieved on rigid and flexible substrates, respectively. The F127 passivation strategy provides an effective approach for fabricating high-efficiency and stable PSCs.
关键词： flexible solar cells,block copolymer,perovskite solar cells,interface passivation,stability
更新于2025-10-22 19:40:53
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Fabrication of highly efficient and stable hole‐transport material free perovskite solar cells through morphology and interface engineering: full ambient process
摘要： Carbon based hole-transport material (HTM) free perovskite solar cells (PVSCs) with low cost and high stability have attracted research interests. Here, we report a facile way to improve the performance of HTM free PVSCs by employing two strategies: firstly, adding a small amount of tetrahydrofuran (THF) in lead iodide (PbI2)/N,N-dimethylformamide (DMF) solution to improve the quality of perovskite film; secondly, introducing an ultra-thin Al2O3 film at the interface of TiO2/perovskite to reduce charge recombination. THF is found to facilitate the formation of homogenous perovskite films with better coverage, while the ultra-thin Al2O3 layer will avoid the direct contact of TiO2 with CH3NH3PbI3. The Al2O3 layer can effectively block holes and prevents charge recombination, thus lead to a dramatic improvement of open circuit voltage and fill factor in PVSCs. Moreover, our PVSCs show excellent long term stability with no degradation for 1000 hours under ambient conditions. We provide a facile way for the future commercialization of efficient low-cost HTM-free PVSCs.
关键词： hole conductor free,interface engineering,perovskite solar cells,high stability
更新于2025-10-22 19:40:53
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Fascinating Physical Properties of 2D Hybrid Perovskite [(NH3)(CH2)7(NH3)]CuClxBr4?x, x?=?0, 2 and 4
摘要： The 2-D organic–inorganic hybrid perovskites of the formula [(NH3)(CH2)7(NH3)]CuClxBr4?x, x = 0, 2 and 4 were prepared by slow evaporation from ethanolic solution in stoichiometric ratio 1:1 (organic/inorganic). Microchemical analysis and x-ray diffraction (XRD) were used to confirm the formation of the presently investigated hybrids. Differential scanning calorimetry (DSC) indicated order–disorder transitions at T1 = 357 K, T2 = 388 K, and T3 = 398 K for x = 0, 2 and 4 of the three heptane diammonium Cu hybrid perovskites, respectively. These transitions are in good agreement with the electrical permittivity results at different frequencies and temperatures. Optical properties and estimated band gap energy reveal that the band gap energy decreases sharply with replacement of Cl ion by Br ion where the band gap energy of [(NH3)(CH2)7(NH3)]CuBr4, x = 0 (denoted 2C7CuBr) is 1.6 eV (brown color) and for [(NH3)(CH2)7(NH3)]CuCl4, x = 4 (denoted 2C7CuCl) is 2.6 eV (yellow color). The differential magnetic susceptibility of 2C7CuBr in the temperature range 80–300 K indicates the effective magnetic moment μeff = 2.05 BM.
关键词： 2D hybrid perovskite,optical properties of halide perovskite,phase transition,magnetic properties of Cu perovskite
更新于2025-09-23 15:23:52
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Caesium-Incorporated Triple Cation Perovskites Deliver Fully Reversible and Stable Nanoscale Voltage Response
摘要： Perovskite solar cells that incorporate small concentrations of Cs in their A-site have shown increased lifetime and improved device performance. Yet, the development of fully stable devices operating near the theoretical limit requires understanding how Cs influences perovskites’ electrical properties at the nanoscale. Here, we determine how the chemical composition of three perovskites (MAPbBr3, MAPbI3, and Cs-mixed) affects their short- and long-term voltage stabilities, with <50 nm spatial resolution. We map an anomalous irreversible electrical signature on MAPbBr3 at the mesoscale, resulting in local Voc variations of ~400 mV, and in entire grains with negative contribution to the Voc. These measurements prove the necessity of high spatial resolution mapping to elucidate the fundamental limitations of this emerging material. Conversely, we capture the fully reversible voltage response of Cs-mixed perovskites, containing small amounts of Cs, FA, and Br, demonstrating that the desired electrical output persists even at the nanoscale. The Cs-mixed material presents no spatial variation in Voc, as ion motion is restricted. Our results show that the nanoscale electrical behavior of the perovskites is intimately connected to their chemical composition and macroscopic response.
关键词： ion motion,MAPbI3,Cs-mixed perovskite,MAPbBr3,nanoscale voltage,perovskite solar cells,Kelvin probe force microscopy
更新于2025-09-23 15:23:52
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Multi-active sites derived from a single/double perovskite hybrid for highly efficient water oxidation
摘要： The oxygen evolution reaction (OER) plays a crucial role in the application of water splitting, which is a highly competitive option for a sustainable energy future. Thus, it is vital to design highly active and durable electrocatalyst for OER. Herein a hybrid with the nominal composition of Ba2Co1.5Mo0.25Nb0.25O6-d (denoted as BC1.5MN) electrocatalyst consisting of both double perovskite and single perovskite structures is synthesized by a solid-state reaction method. When tested as an electrocatalyst for OER, the BC1.5MN electrocatalyst requires a current density of 10 mA cm-2 at an overpotential of 400 mV, an onset overpotential of 260 mV, and a Tafel slope of 70 mV dec-1, which are superior to that of precious metal oxide IrO2 catalyst. Chronoamperometric and cyclic voltammetry studies demonstrate that the BC1.5MN electrocatalyst has outstanding durability in alkaline solution. The synergistic effect between multi-active sites derived from a single/double perovskite hybrid structure results in one of the most active perovskite-based OER electrocatalysts in alkaline solution.
关键词： hybrid,oxygen evolution reaction,double perovskite,single perovskite,electronic structure
更新于2025-09-23 15:23:52
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Spectrally Resolved Ultrafast Exciton Transfer in Mixed Perovskite Quantum Wells
摘要： Solution-processed perovskite quantum wells have been used to fabricate increasingly efficient and stable optoelectronic devices. Little is known about the dynamics of photogenerated excitons in perovskite quantum wells within the first few hundred femtoseconds – a crucial timescale on which energy and charge transfer processes may compete. Here we use ultrafast transient absorption and two-dimensional electronic spectroscopy to clarify the movement of excitons and charges in reduced-dimensional perovskite solids. We report excitonic funneling from strongly to weakly confined perovskite quantum wells within 150 fs, facilitated by strong spectral overlap and orientational alignment among neighboring wells. This energy transfer happens on timescales orders of magnitude faster than charge transfer, which we find to occur instead over 10 - 100s of picoseconds. Simulations of both F?rster-type interwell exciton transfer and free carrier charge transfer are in agreement with these experimental findings, with theoretical exciton transfer calculated to occur in 100s of fs.
关键词： energy transfer,Carrier,metal halide perovskite,two-dimensional electronic spectroscopy,layered perovskite,dynamics
更新于2025-09-23 15:23:52
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Computational Study of Perovskite Structured CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> and CH<sub>3</sub>NH<sub>3</sub>SnI<sub>3</sub>
摘要： Nowadays, Hybrid Perovskite materials perform a major role in solar cell industry due to their superior power conversion ability. CH3NH3PbI3 is the prominent material in hybrid perovskite, where they comprised with advanced photovoltaic properties. But considering the toxicity, it’s more important to observe the role of metal atom in hybrid perovskite. Therefore, this research is basically focused on the objective of figuring out the fundamental properties of CH3NH3PbI3 and CH3NH3SnI3 with the idea of replacing Pb to Sn in future. Ab-Initio Simulation has been used throughout this research along with basic density function theories (DFT) like Exchange correlation functional, Local-density approximation of Kohn-Sham theory. Moreover, the research was also focused upon the Energy band gap variation, crystallographic orientations, density of states in P, S orbitals of cubic and tetragonal phases in CH3NH3PbI3 and CH3NH3SnI3.
关键词： Energy Bands,Methyl ammonium Tin Iodide perovskite,Density Function Theory,Methyl ammonium lead Iodide,Perovskite structure
更新于2025-09-23 15:23:52
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Self-Patterned CsPbBr3 Nanocrystals for High-Performance Optoelectronics
摘要： All-inorganic lead halide perovskites are promising materials for many optoelectronic applications. However, two issues that arise during device fabrication hinder their practical use, namely inadequate continuity of coated inorganic perovskite films across large areas and inability to integrate these films with traditional photolithography due to poor adhesion to wafers. Herein, for the first time, to address these issues, we show a room-temperature synthesis process employed to produce CsPbBr3 perovskite nanocrystals with two-dimensional (2D) nanosheet features. Due to the unique properties of these 2D nanocrystals, including the 'self-assembly' characteristic, and 'double solvent evaporation inducing self-patterning' strategy are used to generate high-quality patterned thin films in selected areas automatically after-drop-casting, enabling fabrication of high-performance devices without using complex and expensive fabrication processing techniques. The films are free from micro-cracks. In a proof-of-concept experiment, photodetector arrays are used to demonstrate the superior properties of such films. We provide evidence of both high responsivity (9.04 A/W) and high stability across large areas. The photodetectors fabricated on flexible substrate exhibit outstanding photo-response stability. Advanced optical and structural studies reveal the possible mechanism. Our simple and cost-effective method paves the way for the next-generation nanotechnology based on high-performance, cost-effective optoelectronic devices.
关键词： photodetector,Self-assembly,self-patterning,two-dimensional nanosheet,perovskite
更新于2025-09-23 15:23:52
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Stark Effect and Environment-Induced Modulation of Emission in Single Halide Perovskite Nanocrystals
摘要： Organic-inorganic halide perovskites have emerged as promising materials for next generation solar cells. In nanostructured form also, these materials are excellent candidates for optoelectronic applications such as lasers and light emitting diodes for displays and lighting. While great progress has been achieved so far in optimizing the intrinsic photophysical properties of perovskite nanocrystals (NCs), in working opto-electronic devices external factors, such as the effects of conducting environment and of the applied electric field on exciton generation and photon emission have been largely unexplored. Here, we use NCs of the all-inorganic perovskite CsPbBr3 dispersed polyvinyl carbazole, a hole-conductor, and in polymethyl methacrylate, an insulator, to examine the effects of applied electric field and conductivity of the matrix on the perovskite photophysics at single-particle level. We found that the conducting environment causes a significant decrease of photoluminescence (PL) brightness of individual NCs due the appearance of intermediate-intensity emitting states with significantly shortened lifetime. Applied electric field has a similar effect and, in addition, causes a non-linear spectral-shift of the PL maxima, a combination of linear and quadratic Stark effect caused by environment-induced polarity and field-related polarizability. The environment and electric field effects are explained by ionization of the NCs through hole transfer and emission of the resulting negatively-charged excitons.
关键词： ionization,halide perovskite nanocrystals,single-particle spectroscopy,Stark effect,blinking
更新于2025-09-23 15:23:52
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Structural characterization of bulk and nanoparticle lead halide perovskite thin films by (S)TEM techniques
摘要： Lead halide (APbX3) perovskites, in polycrystalline thin films but also perovskite nanoparticles (NPs) have demonstrated excellent performances to implement a new generation of photovoltaic and photonic devices. The structural characterization of APbX3 thin films using (scanning) transmission electron microscopy ((S)TEM) techniques can provide valuable information that can be used to understand and model their optoelectronic performance and device properties. However, since APbX3 perovskites are soft materials, their characterization using (S)TEM is challenging. Here, we study and compare the structural properties of two different metal halide APbX3 perovskite thin films: bulk CH3NH3PbI3 prepared by spin-coating of the precursors in solution and CsPbBr3 colloidal NPs synthetized and deposited by doctor blading. Both specimen preparation methods and working conditions for analysis by (S)TEM are properly optimized. We show that CH3NH3PbI3 thin films grown by a one-step method results in the formation of tetragonal perovskite thin films with good adherence to an underlying TiO2 layer, which is characterized by a photoluminescence (PL) emission band centered at 775 nm. The perovskite thin films based on CsPbBr3 colloidal NPs, which are used as the building blocks of the film, they are preserved by the deposition process, even if small gaps are observed between adjacent NPs. The crystal structure of CsPbBr3 NPs is cubic, which is beneficial for optical properties due to its optimal band gap. The absorption and PL spectra measured in both the thin film and the colloidal solution of CsPbBr3 NPs are very similar, indicating a good homogeneity of the thin films and the absence of aggregation of NPs. However, a particular care was required to avoid long electron irradiation times during our structural studies, even at a low voltage of 80 kV, as the material was observed to decompose through Pb segregation.
关键词： structural characterization,TEM,thin films,optoelectronics,STEM,nanoparticles,perovskite
更新于2025-09-23 15:23:52