Electronegativity explanation on the efficiency-enhancing mechanism of the hybrid inorganic–organic perovskite ABX ₃ from first-principles study

Organic–inorganic hybrid perovskites play an important role in improving the efficiency of solid-state dye-sensitized solar cells. In this paper, we systematically explore the efficiency-enhancing mechanism of ABX 3 ( A = CH 3 NH 3 ; B = Sn, Pb; X = Cl, Br, I) and provide the best absorber among ABX 3 when the organic framework A is CH 3 NH 3 by first-principles calculations. The results reveal that the valence band maximum (VBM) of the ABX 3 is mainly composed of anion X p states and that conduction band minimum (CBM) of the ABX 3 is primarily composed of cation B p states. The bandgap of the ABX 3 decreases and the absorptive capacities of different wavelengths of light expand when reducing the size of the organic framework A , changing the B atom from Pb to Sn, and changing the X atom from Cl to Br to I. Finally, based on our calculations, it is discovered that CH 3 NH 3 SnI 3 has the best optical properties and its light-adsorption range is the widest among all the ABX 3 compounds when A is CH 3 NH 3 . All these results indicate that the electronegativity difference between X and B plays a fundamental role in changing the energy gap and optical properties among ABX 3 compounds when A remains the same and that CH 3 NH 3 SnI 3 is a promising perovskite absorber in the high efficiency solar batteries among all the CH 3 NH 3 BX 3 compounds.