Computed and Experimental Absorption Spectra of the Perovskite CH3NH3PbI3.
Electronic structure and light absorption properties of the perovskite CH3NH3PbI3 are investigated by relativistic density functional theory with quasiparticle GW corrections and many-body interactions. The nature of the Wannier exciton is studied by solving the Bethe-Salpeter equation augmented with the analysis of a conceptual hydrogen-like model. The computed absorption spectrum unravels a remarkable absorption "gap" between the first two absorption peaks. This discontinuity is maintained in the calculated tetragonal structure that, however, is not stable at low temperature. Most importantly, the discontinuity is also observed in the experimental absorption spectrum of the orthorhombic single crystal at low temperature (4 K). However, in contrast to the single crystal, in a polycrystalline perovskite film at 5 K the "gap" is filled by a monotonously increasing absorption throughout the visible range. This feature of thin films points to the potential significance of defect absorption for the excellent light harvesting properties of perovskite-based solar cells.
†Institute of Advanced Studies and School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798.
Xi
X
Zhu
†Institute of Advanced Studies and School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798.
Haibin
H
Su
‡Noyes Laboratory, California Institute of Technology, Pasadena California 91125, United States.|§School of Physical and Mathematical Sciences, Singapore 637371.
Rudolph A
RA
Marcus
§School of Physical and Mathematical Sciences, Singapore 637371.|∥TUM CREATE, Singapore 138602.
Maria E
ME
Michel-Beyerle
Bethe−Salpeter equation; First-Principles GW Calculations; Methylammonium Lead Iodide; Perovskite; spin−orbit coupling