Electronic and Optical Properties of C₄N₂H₁₄-Based Lead-Less Halide Perovskites Investigated by First Principles

Abstract

Hybrid organic−inorganic lead halide perovskites have attracted great attention since their power conversion efficiencies have been rapidly improved from the initial 3.8% to the current 25.5% efficiency. Fifteen novel C 4 N 2 H 14 -based perovskites, C 4 N 2 H 14 PbX 4 (X = Cl, Br, I) and C 4 N 2 H 14 Pb 1−y B y X 4 (B = Sn, Ge; X = Br, I; y = 0.25, 0.50, 0.75) were investigated using density functional theory toward their stability and electronic and optical properties. The obtained results show that both X-site substitution by Br/I and B-site doping by Sn/Ge on C 4 N 2 H 14 PbCl 4 can tune the band gap without sacrificing the structural and thermodynamic stability. It is also observed that the light harvesting is broadened through Br/I substitution or Sn/Ge doping according to calculations of the dielectric function and absorption coefficient. In summary, the C 4 N 2 H 14 Pb 1−y Sn y I 4 series is expected to have the most potential among all of the studied systems for the absorber layer application in solar cells due to their suitable band gaps, good stabilities, and broad light absorption region. We hope this work is helpful to develop less toxic and high-performance perovskites applied in photovoltaics.