Electronegativity explanation on the efficiency-enhancing mechanism of the hybrid inorganic–organic perovskite ABX3 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 ABX3 (A = CH3NH3; B = Sn, Pb; X = Cl, Br, I) and provide the best absorber among ABX3 when the organic framework A is CH3NH3 by first-principles calculations. The results reveal that the valence band maximum (VBM) of the ABX3 is mainly composed of anion X p states and that conduction band minimum (CBM) of the ABX3 is primarily composed of cation B p states. The bandgap of the ABX3 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 CH3NH3SnI3 has the best optical properties and its light-adsorption range is the widest among all the ABX3 compounds when A is CH3NH3. 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 ABX3 compounds when A remains the same and that CH3NH3SnI3 is a promising perovskite absorber in the high efficiency solar batteries among all the CH3NH3BX3 compounds.