Magnetic Field Effects in Hybrid Perovskite Devices

Solar cells based on the organic-inorganic perovskites (CH$_{3}$NH$_{3}$PbX$_{3}$, X$=$halogen) have reached a remarkable power conversion efficiency approaching 20{\%}, which calls for research studies of the photophysics behind this high device performance. We measured significant magneto-photocurrent (MPC) response in CH$_{3}$NH$_{\mathrm{3}}$PbI$_{\mathrm{3-x}}$Cl$_{\mathrm{x}}$ photovoltaic cells, in the form of Lorentzian up to field $B=$1T. We attribute the MPC(B) response to spin mixing of loosely-bound photogenerated e-h pairs having different $g$-factor (dubbed ``$\Delta g$ mechanism''). We verified this mechanism by measuring $\Delta g$ directly, using the field induced circularly polarized photoluminescence emission at low temperature, along with the photocarriers' lifetime measured by picosecond pump-probe spectroscopy. We conclude that MPC of spin 1/2 e-h pairs provides a promising method for investigating the spin-related properties of photoexcitations in the novel hybrid perovskites.