Energy Tuning of Electronic Spin Coherent Evolution in Methylammonium Lead Iodide Perovskites
G. Garcia‐Arellano, G. Allard, Laurent Legrand, Thierry Barisien, Damien Garrot, Emmauelle Deleporte, F. Bernardot, C. Testelin, M. Chamarro
Abstract
We investigated the coherent evolution of the electronic spin at low temperature in high-quality CH3NH3PbI3 polycrystalline films by picosecond-resolved photoinduced Faraday rotation. We show that this coherent evolution can be tuned by choosing the pump–probe energy within the lowest optical-absorption band, and we explain it as the result of two main contributions: the localized electron and the localized hole. Their corresponding amplitude ratios are not constant across the lowest absorption band—an observation which disqualifies a free exciton from being at the origin of the electronic spin coherent evolution. We measured a spin coherence time of localized electrons (holes) of 4.4 ns (3.7 ns) at 1.635 eV, which evolves to about 7 ns at 1.612 eV (the hole coherence time remains almost constant at lower energies). Finally, we provide a global image of the spin coherent evolution in bulk metal halide perovskite, which overcomes recent controversies.