Hydrogen‐Bond‐Based Polymer‐Ammonium Intermediates Induced Buried Interface Engineering for High‐Performance Inverted Perovskite Solar Cells

Abstract

Perovskite interfaces where defects enrich are pivotal for both device efficiency and stability. Herein, a high‐molecular‐weight polyvinyl pyrrolidone (PVP) is proposed as a robust multi‐functional interlayer to engineer the buried interface. Besides the well‐known defect passivation, perovskite crystallization is intriguingly modulated via the formation of hydrogen‐bond‐based polymer‐ammonium intermediates (e.g., PVP‐FA+ or PVP‐MA+, where MA and FA are methylamine and formamidine, respectively). The interaction energies derived from density functional theory calculations (−34.5, −26.8, and −9.9 kcal mol−1 for PVP‐FA+, PVP‐MA+, and PVP‐Pb2+) suggest that PVP predominately interacts with ammonium cations to form the intermediates, thus largely excluding other chemical interactions and retarding the perovskite crystallization. As such, the hydrophilic PVP interlayer leads to spontaneous perovskite spreading yet a counterintuitively similar nucleation density with respect to the hydrophobic poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine] (PTAA), a change of preferred crystal orientation, improved crystallinity, and remarkably suppressed non‐radiative recombination. These conducive effects jointly minimize the open‐circuit voltage loss and give rise to superior power conversion efficiency for small‐area and large‐area devices.