Publication Type:Journal Article
Source:Nano Letters, Volume 15, Issue 3, p.1553-1558 (2015)
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 Pini \~ 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°/μm at 200 K (at wavelength λ = 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.