Electronic Structure and Optical Properties of Gallium-Doped Hybrid Organic-Inorganic Lead Perovskites from First-Principles Calculations and Spectroscopic Limited Maximum Efficiencies

Low cost and ultrahigh power conversion efficiencies of the hybrid organic-inorganic lead perovskites have brought a revolution among the solar cell researchers never seen before. However, stability and toxicity are the major concerns hindering it from getting commercialized. Compositional engineering by employing mixed metal cations and halides has become one of the efficient way to tackle these problems. Taking this route, the structural, electronic, and optical properties of Ga-doped tetragonal MAPbI(3) perovskites have been investigated with generalized gradient approximation using density functional theory. Structural analysis such as doping effects on the lattice volume, bond length, tilting angles, and enthalpies of formation have been calculated and detailed analysis are reported. Band-structure calculations have been performed with and without spin-orbit coupling (SOC) in which impurity bands were observed in the case of the doped structures. Other electronic properties such as effective masses and projected density of states have also been calculated and discussed in depth. For light harvesting, necessary optical properties, viz. dielectric function, refractive index, extinction coefficient, absorption coefficient, and reflectivity, were also computed. From the optical properties, blue-shift behavior was observed, which is found to be consistent with the calculated electronic properties. Lastly, using SLME method, it was found that MAPbI(3) with 6.25% Ga dopant concentration has the highest efficiency among all the investigated perovskite materials. All the parameters were calculated and compared with available experimental and reported values and found to be in fairly good agreement.