GW quasiparticle band gap of the hybrid organic-inorganic perovskite CH3NH3PbI3: Effect of spin-orbit interaction, semicore electrons, and self-consistency

We study the quasiparticle band gap of the hybrid organic-inorganic lead halide perovskite CH3NH3PbI3, using many-body perturbation theory based on the GW approximation. We perform a systematic analysis of the band gap sensitivity to relativistic spin-orbit effects, to the description of semicore Pb-5d and I-4d electrons, and to the starting Kohn-Sham eigenvalues. We find that the inclusion of semicore states increases the calculated band gap by 0.2 eV, and self-consistency on the quasiparticle eigenvalues using a scissor correction increases the band gap by 0.5 eV with respect to the G(0)W(0) result. These findings allow us to resolve an inconsistency between previously reported GW calculations for CH3NH3PbI3. Our most accurate band gap is 1.72 eV, and is in good agreement with the measured optical gap after considering a small excitonic shift as determined in experiments.