Electronic and Optical Properties of Sn/Ge-Substituted 2D Dion-Jacobson Phase (3-AMPY)₄Pb₄I₁₆ Perovskite for Photovoltaic Applications: A First Principle Study

The structural, electronic, optical, and photovoltaic properties of Sn/Ge-substituted 2D slightly shifted DJ phase (3-AMPY)4Pb4I16 perovskite were investigated using first principle calculations. The toxic Pb was substituted in the primary geometry by less toxic Sn/Ge. We found that Ge/Sn doping is energetically favorable for decreasing and eliminating the Pb content in pristine (3-AMPY)4Pb4I16. On both Ge/Sn doping critical characteristics for perovskite, strong optical absorption, p–p/s-p couplings, and direct band gap are observed. The strong p–p/s-p couplings in both Ge/Sn-substituted conformers decrease the band gap of the pristine (3-AMPY)4Pb4I16 to the value suitable for photovoltaic applications. This further helps us get good optical absorption coefficient and high-power conversion efficiency in (3-AMPY)4Pb4–xGexI16 (x = 1, 2, 3, 4) and (3-AMPY)4Ge4–xSnxI16 conformers. The partial density of states and band structure plots show significant contributions of the dominant organic cation to the conduction band minimum. This contribution becomes more pronounced with increasing Ge/Sn doping. The presence of Ge/Sn dopant atoms in the substituted 2D (3-AMPY)4Pb4I16 perovskite showed improved photovoltaic performance compared to that of the pristine system. This study should form a basis for realizing a more benign photovoltaic perovskite-based system.