Emerging solar technologies: Perovskite solar cell

Phase Transitions and Electric Properties of PbBr2 under High Pressure: A First-Principles Study

PbBr₂ has recently attracted considerable attention as a precursor for lead halide perovskite-based devices because of its attractive properties. It is known that pressure can modify the chemical and physical properties of materials by altering the distance between atoms in the lattice. Here, a global structure-searching scheme was used to explore the high-pressure structures of PbBr₂, whose structures and properties at high pressure are still far from clear. Three new phases of PbBr₂ were predicted in the pressure range of 0-200 GPa, and the pressure-driven phase transition sequence of orthorhombic Pnma (0-52 GPa) → tetragonal I4/mmm (52-80 GPa) → orthorhombic Cmca (80-153.5 GPa) → orthorhombic Immm (153.5-200 GPa) is proposed. Electronic calculations indicate a semiconductor-to-metallic transition of PbBr₂ in the Cmca phase at ~120 GPa. Our present results could be helpful in improving the understanding of fundamental physical properties and provide insights to modulate the structural and related photoelectric properties of PbBr₂.

Pressure effect on structures and optoelectronic attributes of mixed halide CsPb(I/Br)3: a density functional theory study

The effect of pressure (up to 10 GPa) on the electronic and optical properties of bromine-substituted cesium lead iodide (CsPbI₃), as one promising inorganic halide perovskite, is investigated using modified Backe-Johnson (mBJ) potential for the first time to our knowledge. The lattice parameters, electronic bandgap, and imaginary and real parts of the dielectric function, along with the optical absorption coefficient, are calculated. Density functional perturbation theory is employed to compute the optical properties in the photon energy range from 0.0 to 30 eV. No structural or phase-type transformation is noticed under the applied pressure, which resulted in a uniform contraction of the unit cell. Bandgap variation is seen in all the structures, with the maximum (1.65 eV) and minimum (1.46 eV) decrease found for doped and undoped CsPbBrI₂, respectively. The present work provides useful information about the performance of CsPbI_3-xBr_x compounds under high pressure that can be utilized in designing solar cells and optoelectronics.

Calculation of electronic and optical properties of methylammonium lead iodide perovskite for application in solar cell

Organic-inorganic metal halide perovskite materials, i.e., ABX3 (A = methylammonium, B = Pb, X = Cl, Br, I) have been proved to be outstanding for solar energy conversion. They provide a solution to renewable energy problems with good efficiency and cost-effective technology. Here, we report the initial calculations done by solving Kohn-Sham equations by the use of density function theory. The electronic structural and band gap of CH3NH3PbI3 material are obtained by using different exchange-correlation potential (PBE, PBE-sol, GGA). Further, solar cell devices with CH3NH3PbI3 as absorption layer and CdS/TiO2/ZnTe as buffer layer have been modeled; device physics is discussed and performance of solar cell structure is analyzed in terms of short circuit current density, open circuit voltage, efficiency, fill factor, and quantum efficiency. The maximum efficiency of CH3NH3PbI3 solar cell is found to be 19.6% with TiO2 buffer layer, whereas efficiency with ZnTe buffer layer is also comparable which is 19.5%. Further the effect of layer thickness and temperature are analyzed for maximum efficiency.

A Review on Lead-Free Hybrid Halide Perovskites as Light Absorbers for Photovoltaic Applications Based on Their Structural, Optical, and Morphological Properties

Despite the advancement made by the scientific community in the evolving photovoltaic technologies, including the achievement of a 29.1% power conversion efficiency of perovskite solar cells over the past two decades, there are still numerous challenges facing the advancement of lead-based halide perovskite absorbers for perovskite photovoltaic applications. Among the numerous challenges, the major concern is centered around the toxicity of the emerging lead-based halide perovskite absorbers, thereby leading to drawbacks for their pragmatic application and commercialization. Hence, the replacement of lead in the perovskite material with non-hazardous metal has become the central focus for the actualization of hybrid perovskite technology. This review focuses on lead-free hybrid halide perovskites as light absorbers with emphasis on how their chemical compositions influence optical properties, morphological properties, and to a certain extent, the stability of these perovskite materials.