First-principles analysis of the structural, electronic, and elastic properties of cubic organic–inorganic perovskite HC(NH2)2PbI3 *

The structural, electronic, and elastic properties of cubic HC(NH2)(2)PbI3 perovskite are investigated by density functional theory using the Tkatchenko-Scheffler pairwise dispersion scheme. Our relaxed lattice parameters are in agreement with experimental data. The hydrogen bonding between NH2 and I ions is found to have a crucial role in FAPbI(3) stability. The first calculated band structure shows that HC(NH2)(2)PbI3 has a direct bandgap (1.02 eV) at R-point, lower than the bandgap (1.53 eV) of CH3NH3PbI3. The calculated density of states reveals that the strong hybridization of s(Pb)p(I) orbital in valence band maximum plays an important role in the structural stability. The photo-generated effective electron mass and hole mass at R-point along the R-G and R-M directions are estimated to be smaller: m(e)* = 0.06m(0) and m(h)* = 0.08m(0) respectively, which are consistent with the values experimentally observed from long range photocarrier transport. The elastic properties are also investigated for the first time, which shows that HC(NH2)(2)PbI3 is mechanically stable and ductile and has weaker strength of the average chemical bond. This work sheds light on the understanding of applications of HC(NH2)(2)PbI3 as the perovskite in a planar-heterojunction solar cell light absorber fabricated on flexible polymer substrates.