Interface molecular orientation engineering-induced field reversal for efficient inverted perovskite solar cells

Abstract

Inverted perovskite solar cells (PSCs) continue to suffer from severe non-radiative recombination and low carrier transport at the perovskite/C₆₀ interface. Traditional passivation layers typically improve the device's open-circuit voltage while compromising its short-circuit current density and fill factor. To simultaneously address these issues, a multifunctional organic ammonium salt, 2-(4-(aminomethyl)phenyl)ethyl-1-ammonium iodide (PMEAI), was strategically incorporated at the perovskite/C₆₀ interface. The horizontally aligned PMEAI suppressed both Pb- and I-vacancy defects and induced a reversal of the built-in electric field at the perovskite/C₆₀ interface, effectively minimizing interfacial recombination losses. More importantly, it exhibited minimal molecular steric hindrance, accelerating carrier transport. The resultant PSCs achieve a power conversion efficiency (PCE) of 26.7% (certified PCE: 25.84%). It also obtained a remarkable PCE of 24.5% in a 1 cm² active area. The broad applicability of PMEAI as a passivation layer enabled high-performance wide-bandgap PSCs with 23.0% efficiency. Furthermore, the redirected electric field, oriented from C₆₀ toward the perovskite, suppresses Ag⁺ ion migration from the electrode into the perovskite layer, thereby significantly enhancing operational stability. The PMEAI-treated devices retain 97% of their initial efficiency after 1500 h under ISOS-L-2 protocols and exhibit negligible degradation following 1344 h of ISOS-D-1 aging.