First-Principles Calculation of the Bulk Photovoltaic Effect in CH₃NH₃PbI₃ and CH₃NH₃PbI3–xClx

Hybrid halide perovskites exhibit nearly 20% power conversion efficiency, but the origin of their high efficiency is still unknown. Here, we compute the shift current, a dominant mechanism of the bulk photovoltaic (PV) effect for ferroelectric photovoltaics, in CH 3 NH 3 PbI 3 and CH 3 NH 3 PbI 3– x Cl x from first-principles. We find that these materials give approximately three times larger shift current PV response to near-IR and visible light than the prototypical ferroelectric photovoltaic BiFeO 3 . The molecular orientations of CH 3 NH 3 + can strongly affect the corresponding PbI 3 inorganic frame so as to alter the magnitude of the shift current response. Specifically, configurations with dipole moments aligned in parallel distort the inorganic PbI 3 frame more significantly than configurations with near-net-zero dipole, yielding a larger shift current response. Furthermore, we explore the effect of Cl substitution on shift current and find that Cl substitution at the equatorial site induces a larger response than does substitution at the apical site.