Photo-energy conversion efficiency of CH3NH3PbI3/C60 heterojunction perovskite solar cells from first-principles

Abstract

Halide perovskites have emerged as the most potential candidate for the next-generation solar cells. In this work, we conduct a comprehensive first-principles study on the photo-energy conversion efficiency (PCE) of the CH3NH3PbI3/C60 heterojunction. Since perovskite solar cells (PSCs) are generally exposed to substantial temperature variations that affect the photo-physics and charge separation in the perovskites, finite slabs of both the tetragonaland cubic-phases of CH3NH3PbI3 (MAPbI3) are constructed with different orientations of the methylammonium (MA) cation with respect to the perovskite surface. A C60 molecule, acting as an electron acceptor and transport material, is introduced at various positions on the MAPbI3 surface. Using the detailed balance approach, the PCE of the heterojunction is determined by examining the Kohn–Sham energies and orbitals located either in MAPbI3 or in C60. Our study reveals that the stability, the exciton dissociation efficiency, and the PCE of the tetragonal MAPbI3/C60 heterojunctions strongly depend on the MA orientation and the C60 position on the MAPbI3 surface. This is attributed to the polar behavior of MAPbI3. Using the tetragonal-phase heterojunction, a high PCE of Z B 19% can be achieved, if certain surface conditions are met. Built-in electric field originating from the surface dipoles of the MA cation facilitates the dissociation of electron– hole pairs and the electron transfer to fullerene. On the other hand, the heterojunction with a hightemperature cubic MAPbI3 structure exhibits a PCE of Z B 10%, regardless of the MA orientation and C60 on the MAPbI3 surface.