Highly spin-polarized carrier dynamics and ultralarge photoinduced magnetization in CH₃NH₃PbI₃ perovskite thin films

Low-temperature solution-processed organic-inorganic halide perovskite CH₃NH₃PbI₃ has demonstrated great potential for photovoltaics and light-emitting devices. Recent discoveries of long ambipolar carrier diffusion lengths and the prediction of the Rashba effect in CH₃NH₃PbI₃, that possesses large spin-orbit coupling, also point to a novel semiconductor system with highly promising properties for spin-based applications. Through circular pump-probe measurements, we demonstrate that highly polarized electrons of total angular momentum (J) with an initial degree of polarization P_ini ∼ 90% (i.e., -30% degree of electron spin polarization) can be photogenerated in perovskites. Time-resolved Faraday rotation measurements reveal photoinduced Faraday rotation as large as 10°/m at 200 K (at wavelength γ = 750 nm) from an ultrathin 70 nm film. These spin polarized carrier populations generated within the polycrystalline perovskite films, relax via intraband carrier spin-flip through the Elliot-Yafet mechanism. Through a simple two-level model, we elucidate the electron spin relaxation lifetime to be ∼7 ps and that of the hole is ∼1 ps. Our work highlights the potential of CH₃NH₃PbI₃ as a new candidate for ultrafast spin switches in spintronics applications.