Relativistic origin of slow electron-hole recombination in hybrid halide   perovskite solar cells
  The hybrid perovskite CH3NH3PbI3 (MAPI) exhibits long minority-carrier lifetimes and diffusion lengths. We show that slow recombination originates from a spin-split indirect-gap. Large internal electric fields act on spin-orbit-coupled band extrema, shifting band-edges to inequivalent wavevectors, making the fundamental gap indirect. From a description of photoluminescence within the quasiparticle self-consistent GW (QSGW) approximation for MAPI, CdTe and GaAs, we predict carrier lifetime as a function of light intensity and temperature. At operating conditions we find radiative recombination in MAPI is reduced by a factor of more than 350 compared to direct gap behavior. The indirect gap is retained with dynamic disorder. 
Pooya Azarhoosh, Jarvist M. Frost, Scott McKechnie, Aron Walsh and   Mark van Schilfgaarde
cond-mat.mtrl-sci