Electronic structure and photoabsorption property of pseudocubic perovskites CH sub(3)NH sub(3)PbX sub(3)(X = I, Br) including van der Waals interaction

Using density functional theory with the inclusion of van der Waals (vdW) interaction, we have investigated electronic energy bands, density of states, effective masses of charge carriers, and photoabsorption coefficients of pseudocubic CH sub(3)NH sub(3)PbX sub(3) (X = I, Br). Our results confirm the direct band gap of 1.49 (1.92) eV for X = I (Br) in the pseudocubic Pm phase with lattice constant of 6.324 (5.966) Aa, being agreed well with experiment and indicating the necessity of vdW correction. The calculated photoabsorption coefficients for X = I (Br) have the onset at red (orange) color and the first peak around violet (ultraviolet) color in overall agreement with the experiment.