Electronic and Photovoltaic Properties of Superlattices Constructed by Organic–Inorganic Perovskites: a Theoretical Perspective

Perovskite solar cells (PSCs) with ever-increasing power conversion efficiency (PCE) have received enormous attention over the past decade, but long-term stability is still a great challenge in practical applications. Constructing a superlattice by different perovskites is an effective approach for improving the stability and photovoltaic performance of PSCs. Herein, we report the first-principles calculations on geometric, electronic, and optoelectronic properties of superlattice structures composed of conventional perovskites MAPbI3, FAPbI3, and MAPbI2Br. Our calculated formation enthalpies and binding energies show that superlattice formations are exothermic processes, meaning that superlattice perovskites exhibit thermodynamic stability. The bandgaps of superlattices can be fine-tuned by the thickness of the pristine perovskite layers. The states at valence band maximum and conduction band minimum of superlattices are separated on different atomic layers, which can reduce the electron–hole recombination and is conducive to the separation and collection of charge carriers. Small effective masses of carriers and low exciton binding energies give rise to a high density, high mobility, and long lifetime of carriers in the superlattice perovskites. The estimated theoretical PCE of the superlattice reaches as high as 21.62%. This research offers a complementary strategy for designing more stable and efficient light-absorbing materials of PSCs.