Photoexcited Carrier Spin Dynamics in Metal Halide Perovskites

Dr. Yan Li
Department of Physics and Astronomy
University of Utah

The metal halide perovskites have emerged as a highly promising class of semiconductors for photovoltaic applications. Recently they have shown great promise for the field of spintronics due to their large tunable spin-orbit coupling, spin dependent optical selection rules and predicted electrically tunable Rashba band. I will present our latest study of carrier spin dynamics on the solution processed polycrystalline methylammonium lead halide films. Our experiments of time-resolved Faraday rotation and Hanle effect demonstrated the optical spin orientation of carriers and detection of their spin polarization, which confirms the spin sensitive optical transitions. The energy dependence of the Faraday rotation follows the exciton absorption band at low temperatures, implying its excitonic origin. The results revealed unexpected long spin lifetimes exceeding 1 ns at 4K, given that Pb and I exhibit large spin-orbit coupling, and usually lead to fast spin relaxation. Applic! ation of a transverse magnetic field causes spin precession at two distinct frequencies, indicating two spin components with different g-factors. Power dependence and temperature dependence of the spin lifetimes reveals some clues to the spin relaxation mechanisms.