Prof Henry Snaith FRS

Abstract:

Improving the bulk quality of perovskite films is critical for achieving higher-performance photovoltaic devices. Chloride-containing additives, including lead chloride (PbCl₂) and methylammonium chloride (MACl)—standard additives widely adopted in perovskite photovoltaics—are effective for controlling crystallisation kinetics and grain morphology. However, the distinct impacts of different forms of chloride additives on nanoscale phase uniformity and luminescence homogeneity remains underexplored. Here, we provide new insights into how the choice and combination of chloride additives influence phase transitions and spatially uniform carrier dynamics within perovskite films. We demonstrate that strategically combining MACl and PbCl2 improves crystallinity and optoelectronic uniformity across dimensions spanning micrometres to millimetres. Leveraging these findings, we fabricated inverted (p-i-n) perovskite solar cells achieving certified quasi-steady-state efficiencies of 26.4% and 24.5% at device areas of 0.05 and 1 cm², respectively. Furthermore, these devices exhibit robust operational stability, retaining 88% of their initial performance after 1200 hours of continuous maximum power point tracking at elevated temperatures (65 °C) under simulated AM1.5G illumination. Our results elucidate the mechanistic differences between chloride additive forms, providing a viable strategy for advancing large-area, high-efficiency, and thermally stable perovskite photovoltaics.