Optical absorption coefficient red shift effect of iodine vacancy in MAPbI3

Abstract The Density Function Theory with van der Waals correction are employed to investigate the materials of CH 3 NH 3 PbI 3 (MAPbI 3 ). For the two phases of tetragonal and orthorhombic, the high optical absorption coefficients (OAC) result from electrons jumping from I 5 p to the Pb 6 p near the Fermi level. The two different kinds of iodine vacancy result in the doping energy band appearing in the band gap, and the doping energy band is from Pb 6 p electrons mainly, which is below the Fermi level. The iodine vacancy result in the red shift of OAC, which result in the optical absorption of MAPbI 3 with the iodine vacancy locating in the range from 0.5 eV to 1.47 eV, which locate at the infrared ray part occupying 51% of radiant energy of sunlight. And the red shift favors power transfer between sunlight and electric. The red shift of the OAC originate electrons jumping from Pb 6 p (doping energy bands) to Pb 6 p (conduction bands).