Probing the Role of Local Structure in Driving the Stability of Halide Perovskites CH3_3NH3_3PbX3_3

Organic–inorganic lead halide perovskites have rapidly emerged as one of the leading contenders in optoelectronic and photovoltaic technology, but they show stability issues. Among methylammonium (MA) lead bromide and MA lead iodide, the Br counterpart is reported to exhibit improved stability under ambient conditions. However, the underlying fundamentals of such an enhancement are not fully understood. Using temperature-dependent X-ray diffraction and extended X-ray absorption fine structure measurements, we find relatively reduced value of linear coefficient of thermal expansion, elevated Einstein temperature, and reduced dynamic disorder in MAPbBr$_3$ compared to MAPbI$_3$ which implies that a relatively rigid Pb–Br bond offers steric hindrance to the migration of bulky MA ion resulting in improved stability of MAPbBr$_3$

Recent Developments on the Properties of Chalcogenide Thin Films

Chalcogenide thin films have attracted a great deal of attention for decades because of their unique properties. The recent developments on thin film-based supercapacitor applications were reported. As a result of sustained efforts, the experimental findings revealed remarkable properties with enhanced fabrication methods. The properties of perovskite solar cells were discussed in terms of crystal structure and phase transition, electronic structure, optical properties, and electrical properties. Perovskite solar cell has gained attention due to its high absorption coefficient with a sharp absorption edge, high photoluminescence quantum yield, long charge carrier diffusion lengths, large mobility, high defect tolerance, and low surface recombination velocity. The thin film-based gas sensors are used for equally the identification and quantification of gases, and hence should be both selective and sensitive to a required target gas in a mixture of gases. Metal chalcogenide materials are considered excellent absorber materials in photovoltaic cell applications. These materials exhibited excellent absorption coefficient and suitable band gap value to absorb the maximum number of photons from sun radiation. The photovoltaic parameters were strongly dependent on various experimental conditions

Room temperature growth of CH3NH3PbCl3 single crystals by solvent evaporation method

We report a new route to synthesize high-quality, large-size crystals of CH3NH3PbCl3 through proper selection of DSMO-GBL solution via solvent evaporation method at room temperature. A detailed evaluation of the structural, electronic, optical and electrical properties of these crystals was carried out. Our XPS studies suggested that organic-inorganic halide perovskites are sensitive to X-ray-induced damage, and hence, their properties may get altered. Also, photoluminescence studies displayed two peak spectra, indicating coexistence of order-disorder domains of CH3NH3 in the sample. Further observation of low defect concentration and longer diffusion length indicates that crystals grown by the presented method can offer promising solutions for optoelectronic devices

Overview on Different Types of Solar Cells: An Update

Solar energy is free from noise and environmental pollution. It could be used to replace non-renewable sources such as fossil fuels, which are in limited supply and have negative environmental impacts. The first generation of solar cells was made from crystalline silicon. They were relatively efficient, however very expensive because they require a lot of energy to purify the silicon. Nowadays, the production of solar cells has been improved since the first generation (thin-film solar cells, dye-sensitized solar cells, perovskite solar cells, and organic solar cells). In this work, the development of solar cells was discussed. The advantages, limitations, challenges, and future trends of these solar cells were also reported. Lastly, this article emphasized the various practices to promote solar energy and highlighted the power conversion efficiency of the fabricated devices

Overview on Different types of Solar Cells: An Update

Solar energy is free from noise and environmental pollution. It could be used to replace non-renewable sources such as fossil fuels, which are in limited supply and have negative environmental impacts. The first generation of solar cells was made from crystalline silicon. They were relatively efficient, however very expensive because they require a lot of energy to purify the silicon. Nowadays, the production of solar cells has been improved since the first generation (thin-film solar cells, dye-sensitized solar cells, perovskite solar cells, and organic solar cells). In this work, the development of solar cells was discussed. The advantages, limitations, challenges, and future trends of these solar cells were also reported. Lastly, this article emphasized the various practices to promote solar energy and highlighted the power conversion efficiency of the fabricated devices

Self-immobilized Pd nanowires as an excellent platform for a continuous flow reactor: efficiency, stability and regeneration

Despite extensive use of Pd nanocrystals as catalysts, the realization of a Pd-based continuous flow reactor remains a challenge. Difficulties arise due to ill-defined anchoring of the nanocrystals on a substrate and reactivity of the substrate under different reaction conditions. We demonstrate the first metal (Pd) nanowire-based catalytic flow reactor that can be used across different filtration platforms, wherein, reactants flow through a porous network of nanowires (10–1000 nm pore sizes) and the product can be collected as filtrate. Controlling the growth parameters and obtaining high aspect ratio of the nanowires (diameter = ∼13 nm and length > 8000 nm) is necessary for successful fabrication of this flow reactor. The reactor performance is similar to a conventional reactor, but without requiring energy-expensive mechanical stirring. Synchrotron-based EXAFS studies were used to examine the catalyst microstructure and Operando FT-IR spectroscopic studies were used to devise a regenerative strategy. We show that after prolonged use, the catalyst performance can be regenerated up to 99% by a simple wash-off process without disturbing the catalyst bed. Thus, collection, regeneration and redispersion processes of the catalyst in conventional industrial reactors can be avoided. Another important advantage is avoiding specific catalyst-anchoring substrates, which are not only expensive, but also non-universal in nature

Dynamic Structural Evolution and Dual Emission Behavior in Hybrid Organic Lead Bromide Perovskites

The optoelectronic properties of organic lead halide perovskites (OLHPs) strongly depend on their underlying crystal symmetry and dynamics. Here, we exploit temperature-dependent synchrotron powder X-ray diffraction and temperature-dependent photoluminescence to investigate how the subtle structural changes happening in the pure and mixed A-site cation MA1–xFAxPbBr3 (x = 0, 0.5, and 1) systems influences their optoelectronic properties. Diffraction investigations reveal a cubic structure at high temperatures and tetragonal and orthorhombic structures with octahedral distortion at low temperatures. Steady state photoluminescence and time correlated single photon counting study reveals that the dual emission behavior of these OLHPs is due to the direct-indirect band formation. In the orthorhombic phase of MAPbBr3, the indirect band is dominated by self-trapped exciton (STE) emission due to the higher-order lattice distortions of PbBr6 octahedra. Our findings provide a comprehensive explanation of the dual emission behavior of OLHPs while also providing a rationale for previous experimental observations

NiO as Hole Transporting Layer for Inverted Perovskite Solar Cells: A Study of X‐Ray Photoelectron Spectroscopy

Abstract Hygroscopic and acidic nature of organic hole transport layers (HTLs) insisted to replace it with metal oxide semiconductors due to their favorable charge carrier transport with long chemical stability. Apart from large direct bandgap and high optical transmittance, ionization energy in the range of −5.0 to −5.4 eV leads to use NiO as HTL due to good energetic matching with lead halide perovskites. Analyzing X‐ray photoelectron spectroscopic (XPS) data of NiO, it is speculated that p‐type conductivity is related to the NiOOH or Ni2O3 states in the structure and the electrical conductivity can be modified by altering the concentration of nickel or oxygen vacancies. However, it is difficult to separate the contribution from nonlocal screening, surface effect and the presence of vacancy induced Ni3+ ion due to very strong satellite structure in the Ni 2p XPS spectrum of NiO. Thus, an effective approach to analyze the NiO XPS spectrum is presented and the way to correlate the presence of Ni3+ with the conductivity results which will help to avoid overestimation in finding the oxygen‐rich/deficient conditions in NiO