Investigation of structural, electronic, and optical properties of halide perovskites with different amide cations: A first-principles approach

Hybrid halide perovskites (CH3NH3PbI3) 3 NH 3 PbI 3 ) have emerged as an appealing candidate in photovoltaic devices due to their low-cost fabrication and remarkable optical and electronic properties. However, the commercial applications of these perovskites are limited by their instability due to the rapid rotation and orientation of methyl- ammonium cation (CH3NH3+), 3 NH 3 + ), and interaction with PbI2 2 lattice at high temperatures. Since CH3NH3+ 3 NH 3 + can deteriorate structural stability of MAPbI3 3 perovskites, it is possible to use molecular cation design and substitution as a mechanism to enhance the stability and remove this limitation. We here investigate the effect of replacing this cation with other organic cations (HCOHNH2PbI3 2 PbI 3 (FPbI3), 3 ), CH3COHNH2PbI3 3 COHNH 2 PbI 3 (AcPbI3), 3 ), and NH2COHNH2PbI3 2 COHNH 2 PbI 3 (UPbI3)) 3 )) in order to enhance the performance of the perovskites, while also keeping the band gap energy (Eg) g ) in an appropriate range for solar cell applications. The calculations are performed using the full potential linearized augmented plane wave method, providing lattice parameters and the formation energy of the proposed perovskites. Our results indicate that AcPbI3 3 perovskite outperforms the other structures in terms of various optical parameters, such as the absorption coefficient, optical conductivity, and reflectance. The optical and electronic band gaps of the AcPbI3 3 structure and its resonance form (Ac'PbI3) 3 ) are found to be in agreement with each other, proposing them as optically tunable hybrid perovskites in emerging solar cells.