Publication Type:Journal Article
Source:Nano Letters, American Chemical Society, Volume 15, Number 3, p.1553-1558 (2015)
Keywords:Carrier diffusion length, Electron spin polarization, Electron-spin relaxation, Electrospinning, faraday effect, Light emission, Low temperature solutions, Magnetic moments, Magnetoelectronics, Nanotechnology, Perovskite, Photoinduced magnetization, Pinch effect, Polarization, Polycrystalline perovskite, probes, Pump probe, rotation, Semiconductor quantum wells, spin dynamics, spin polarization, temperature, Time-resolved Faraday rotation
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°/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. © 2015 American Chemical Society.
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