Minimizing interfacial energy losses in inverted perovskite solar cells by a dipolar stereochemical 2D perovskite interface

Inverted perovskite solar cells (PSCs) have attracted broad research and industrial interest owing to their suppressed hysteresis, cost-effectiveness, and easy-fabrication. However, the issue of non-radiative recombination losses at the n-type interface between the perovskite and fullerene has impeded further improvement of photovoltaic performance. Here, we modify the n-type interface of FAPbI3 perovskite films by constructing a stereochemical two-dimensional (2D) perovskite interlayer, in which the organic cations comprise both pyridine and ammonium groups. The pyridine N donor can create stable bonding with the surface-uncoordinated Pb on the perovskite, thereby passivating the shallow-level defects and enhancing the air stability of the film. Furthermore, the pyridine N donor also offers a positive polar interface to decrease the surface work function of the perovskite film, enabling n-type modification. Ultimately, we employ a p-i-n photovoltaic (PV) device with the positive dipole interlayer at perovskite/fullerene contact and achieve remarkable photoelectric conversion efficiency (PCE) of 22.0%.