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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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SiO<sub>2</sub> nanoparticle-regulated crystallization of lead halide perovskite and improved efficiency of carbon-electrode based, low temperature planar perovskite solar cells
摘要： SiO2 nanoparticles were used to regulate the crystallizing process of lead halide perovskite film that prepared by the sequential deposition method, which was used in the low temperature processed, carbon-electrode basing, hole-conductor-free planar perovskite solar cells. It was observed that, after adding small amount of SiO2 precursor (1% in volume ratio) into the lead iodide solution, performance parameters of open-circuit voltage, short-circuit current and fill factor were all upgraded, which helped to increase the power conversion efficiency (reverse scan) from 11.44(±1.83)% (optimized at 12.42%) to 14.01(±2.14)% (optimized at 15.28%, AM 1.5G, 100 mW/cm2). Transient photocurrent decay curve measurements showed that, after the incorporation of SiO2 nanoparticles, charge extraction was accelerated, while transient photovoltage decay and dark current curve tests both showed that recombination was retarded. The improvement is due to the improved crystallinity of the perovskite film. X-ray diffraction and scanning electron microscopy studies observed that, with incorporation of amorphous SiO2 nanoparticles, smaller crystallites were obtained in lead iodide films, while larger crystallites were achieved in the final perovskite film. This study implies that, amorphous SiO2 nanoparticles could regulate the coarsening process of the perovskite film, which provides an effective method in obtaining high quality perovskite film.
关键词： SiO2 (61.46.Hk),crystallization(81.10.-h),low temperature(84.60.Jt),perovskite solar cell(88.40.H-),lead iodide(61.82.Rx),carbon-electrode(88.40.HJ)
更新于2025-09-23 15:21:01
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Low-Temperature Aging Provides 22% Efficient Bromine-Free and Passivation Layer-Free Planar Perovskite Solar Cells
摘要： Previous reports of formamidinium/methylamine (FAMA)-mixed halide perovskite solar cells have focused mainly on controlling the morphology of the perovskite film and its interface—for example, through the inclusion of bromine and surface passivation. In this paper, we describe a new processing pathway for the growth of a high-quality bromine-free FAMAPbI3 halide perovskites via the control of intermediate phase. Through low-temperature aging growth (LTAG) of a freshly deposited perovskite film, α-phase perovskites can be seeded in the intermediate phase and, at the same time, prevent beta-phase perovskite to nucleate. After postannealing, large grain-size perovskites with significantly reduced PbI2 presence on the surface can be obtained, thereby eliminating the need of additional surface passivation step. Our pristine LTAG-treated solar cells could provide PCEs of greater than 22% without elaborate use of bromine or an additional passivation layer. More importantly, when using this LTAG process, the growth of the pure alpha-phase FAMAPbI3 was highly reproducible.
关键词： Perovskite solar cells,Bromine-free,Passivation layer,Lead iodide,Aging growth
更新于2025-09-23 15:21:01
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Direct Silicon Heterostructures With Methylammonium Lead Iodide Perovskite for Photovoltaic Applications
摘要： We investigated the formation of photovoltaic (PV) devices using direct n-Si/MAPI (methylammonium lead tri-iodide) two-sided heterojunctions for the first time (as a possible alternative to two-terminal tandem devices) in which charge might be generated and collected from both the Si and MAPI. Test structures were used to establish that the n-Si/MAPI junction was photoactive and that spiro-OMeTAD acted as a “pinhole blocking” layer in n-Si/MAPI devices. Two-terminal “substrate” geometry devices comprising Al/n-Si/MAPI/spiro-OMeTAD/Au were fabricated and the effects of changing the thickness of the semitransparent gold electrode and the silicon resistivity were investigated. External quantum efficiency and capacitance–voltage measurements determined that the junction was one-sided in the silicon—and that the majority of the photocurrent was generated in the silicon, with there being a sharp cutoff in photoresponse above the MAPI bandgap. Construction of band diagrams indicated the presence of an upward valence band spike of up to 0.5 eV at the n-Si/MAPI interface that could impede carrier flow. Evidence for hole accumulation at this feature was seen in both Kelvin-probe transients and from unusual features in both current–voltage and capacitance–voltage measurements. The devices achieved a hysteresis-free best power conversion efficiency of 2.08%, VOC 0.46 V, JSC 11.77 mA/cm2, and FF 38.4%, demonstrating for the first time that it is possible to create a heterojunction PV device directly between the MAPI and n-Si. Further prospects for two-sided n-Si/MAPI heterojunctions are also discussed.
关键词： heterostructures,MAPI/silicon methylammonium lead iodide,methylammonium lead tri-iodide (MAPI),Heterojunctions,silicon
更新于2025-09-23 15:19:57
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Raman scattering obtained from laser excitation of MAPbI3 single crystal
摘要： Finding renewable energy sources is of paramount importance to meet the increasing global energy demand whilst minimizing the impact on the environment. The research community has focused on solar energy as it is endlessly available, and have ranked the methylammonium lead iodide (MAPbI3) as one of the most promising candidate amongst perovskite solar cells. Despite its high efficiency, the MAPbI3 is sensitive to humidity, light, and temperature, its instability affects primarily on the crystalline structure and eventually leads to degradation. Three crystalline structures are known for this material, orthorhombic, tetragonal, and cubic which exist in different temperatures. Here we report on several processes detected from laser excitation of MAPbI3 single crystal at ambient conditions. A phase transition from tetragonal to cubic phase was induced by excitation of over 15 mW laser power. The phases were characterized by LF-Raman and photoluminescence, taken simultaneously with the increase of exciting laser power and the spectral changes were assigned to the structural differences. In addition, Raman stimulation of iodine vapors signal was observed, those vapors were generated from the core of the focus wherein the highest temperature led to degradation. The stimulated Raman phenomenon was enabled due to the unique properties of the MAPbI3 single crystal and revealed viability to use this material for additional applications in other research fields.
关键词： Methylammonium lead iodide,Stimulated Raman,Low frequency Raman,Phase transition,Single crystal
更新于2025-09-23 15:19:57
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Efficient, stable solar cells by using inherent bandgap of α-phase formamidinium lead iodide
摘要： In general, mixed cations and anions containing formamidinium (FA), methylammonium (MA), caesium, iodine, and bromine ions are used to stabilize the black a-phase of the FA-based lead triiodide (FAPbI3) in perovskite solar cells. However, additives such as MA, caesium, and bromine widen its bandgap and reduce the thermal stability. We stabilized the a-FAPbI3 phase by doping with methylenediammonium dichloride (MDACl2) and achieved a certified short-circuit current density of between 26.1 and 26.7 milliamperes per square centimeter. With certified power conversion efficiencies (PCEs) of 23.7%, more than 90% of the initial efficiency was maintained after 600 hours of operation with maximum power point tracking under full sunlight illumination in ambient conditions including ultraviolet light. Unencapsulated devices retained more than 90% of their initial PCE even after annealing for 20 hours at 150°C in air and exhibited superior thermal and humidity stability over a control device in which FAPbI3 was stabilized by MAPbBr3.
关键词： bandgap,perovskite,formamidinium lead iodide,solar cells,thermal stability
更新于2025-09-12 10:27:22
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Investigating the Growth of CH <sub/>3</sub> NH <sub/>3</sub> PbI <sub/>3</sub> Thin Films on RF‐Sputtered NiO <i> <sub/>x</sub></i> for Inverted Planar Perovskite Solar Cells: Effect of CH <sub/>3</sub> NH <sub/>3</sub><sup>+</sup> Halide Additives versus CH <sub/>3</sub> NH <sub/>3</sub><sup>+</sup> Halide Vapor Annealing
摘要： Investigating the low efficiency issue of radio frequency-sputtered nickel oxide (sp-NiOx)-based perovskite solar cells (PSCs) due to a limited understanding of the correlation between perovskite growth and sp-NiOx on the optoelectronic properties and photovoltaic device performance is critical. Herein, the crystallization of methylammonium (MA) lead iodide (MAPbI3) thin film (obtained from stoichiometric precursor ratio) on sp-NiOx is shown, resulting in appearance of residual PbI2 grains. This is in contrast to perovskite growth on solution-processed NiOx. The amount of residual PbI2 is suppressed by 1) adding excess MACl/MAI additives and 2) annealing the perovskite film in MACl/MAI vapor atmosphere. Structural and morphological results reveal significant reduction in the amount of residual PbI2 and enhanced grain size for all the cases while photophysical measurements reveal mitigation of trap/defect sites (within the bulk and at the interfaces) only for MACl/MAI vapor annealing case. As a result, photovoltaic devices exhibit improved performance only for the vapor annealing case. These results elucidate the critical role of maintaining stoichiometric ratio in perovskite and its crystallization on sp-NiOx by eliminating the associated defects (influenced by sp-NiOx) in rendering improved performance, which can be insightful to further enhance the performance of PSCs.
关键词： vapor annealing,lead iodide,solar cells,nickel oxide,perovskite
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Nonlinear Microscopy of Lead Iodide Nanosheets
摘要： Lead iodide (PbI2) is a layered material with unique optical and electrical properties, including direct bandgap in the bulk and a layered crystalline structure, consisting of close-packed Pb atoms sandwiched between two layers of Iodine atoms. Compared to the widely-studied TMDCs, 2D PbI2 is a new type of halide semiconductors with a relatively larger visible bandgap (Eg ～ 2.4 eV) which endows its distinct optical properties. Despite being studied for decades and being used as a precursor for perovskite materials, the recently developed PbI2 nanosheets have shown a great promise for high-performance optoelectronic devices, such as ?exible photodetectors and nanolasers. Such 2D nanosheets also show a great potential for low-dimensional nonlinear optical devices, However, their nonlinear properties are still unexplored, while novel applications of PbI2 nanosheets require careful characterization of their crystalline structure, thickness and nonlinearity. Here we demonstrate the nonlinear microscopy of PbI2 nanosheets using the polarization and thickness dependence of the second harmonic generation (SHG) and third harmonic generation (THG) from solution-grown nanosheets. Our measurements allow to precisely determine their thickness and crystalline orientation with a non-invasive optical technique.
关键词： third harmonic generation,nonlinear microscopy,Lead iodide,second harmonic generation,nanosheets
更新于2025-09-11 14:15:04
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1D Pyrrolidinium Lead Iodide for Efficient and Stable Perovskite Solar Cells
摘要： Due to the superior environmental stability, the utilization of low-dimensional perovskites in organometal halide solar cells (OMHSCs) has been on the sharp increase. Herein, we report a method to in situ form one-dimensional pyrrolidinium lead iodide (1D PyPbI3) atop the photoactive three-dimensional methylammonium lead iodide (3D MAPbI3) using pyrrolidine post-treatment. As compared to the 3D MAPbI3, the 1D PyPbI3 has a wider bandgap and is more environmentally stable, which serves as a tunnelling contact to mitigate charge carrier recombination and robust barrier against environmental degradation when incorporated into OMHSCs. Accordingly, power conversion efficiencies of the resulting MAPbI3 devices were enhanced from an average of 14.86 ± 0.65% to 15.9 ± 0.58% while shelf-life stability was significantly prolonged.
关键词： perovskite solar cell,one-dimensional perovskite,environmental stability,pyrrolidine,photovoltaic performance,pyrrolidinium lead iodide,charge recombination
更新于2025-09-11 14:15:04
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Effects of Electron-Phonon Coupling on Electronic Properties of Methylammonium Lead Iodide Perovskites
摘要： Temperature can have a dramatic effect on the solar efficiency of methylammonium lead iodide (CH3NH3PbI3) absorbers due to changes in the electronic structure of the system even within the range of stability of a single phase. Herein using first principles density functional theory, we investigate the electron band structure of the tetragonal and orthorhombic phases of CH3NH3PbI3 as a function of temperature. The electron-phonon interactions are computed to all orders using a Monte Carlo approach, which is needed considering that the second-order Allen-Heine-Cardona theory in electron-phonon coupling is not adequate. Our results show that the band gap increases with temperature in excellent agreement with experimental results. We verified that anharmonic effects are only important near the tetragonal-cubic phase transition temperature. We also found that temperature has a significant effect on the effective masses and Rashba coupling. At room temperature, electron–phonon coupling is found to enhance the band effective mass by a factor of two, and to diminish the Rashba coupling by the same factor compared to T=0 K values. Our results underscore the significant impact of electron-phonon coupling on electronic properties of the hybrid perovskites.
关键词： Energy Conversion and Storage,Methylammonium Lead Iodide Perovskites,Plasmonics and Optoelectronics,Electron-Phonon Coupling,Electronic Properties
更新于2025-09-10 09:29:36