First-principles calculation of bulk photovoltaic effect in CH$_3$NH$_3$PbI$_3$ and CH$_3$NH$_3$PbI$_{3-x}$Cl$_{x}$

TL;DR

This study uses first-principles calculations to analyze the bulk photovoltaic effect in hybrid halide perovskites, revealing their high shift current response and the influence of molecular orientation and chlorine substitution.

Contribution

It provides the first-principles analysis of shift current in CH3NH3PbI3 and CH3NH3PbI3-xClx, highlighting factors affecting their photovoltaic efficiency.

Findings

Shift current response is about three times larger than in BiFeO3.

Molecular orientation significantly affects the shift current magnitude.

Chlorine substitution at the equatorial site enhances the shift current response.

Abstract

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 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.