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

• Main Authors: Giovanni, David, Ma, Hong, Chua, Julianto, Grätzel, Michael, Ramesh, Ramamoorthy, Mhaisalkar, Subodh, Mathews, Nripan, Sum, Tze Chien
• Other Authors: School of Materials Science & Engineering
• Format: Article
• Language: English
• Published: 2015
• Subjects: DRNTU::Engineering::Materials::Microelectronics and semiconductor materials::Thin films
• Online Access: https://hdl.handle.net/10356/79452; http://hdl.handle.net/10220/25022
• Institution: Nanyang Technological University

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 photo-induced 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 spintronics applications such as ultrafast spin switches, spin aligners or filters and possibly spin-polarized light emitters.