PbI2 Initiated Cross-Linking and Integration of a Polymer Matrix with Perovskite Films: 1000 h Operational Devices under Ambient Humidity and Atmosphere and with Direct Solar Illumination

The instability of organic lead halide perovskites such as MAPbI3 under ambient conditions is a challenge, as it leads to degradation in device performance and has limited their long-term application. To address this, we use the Lewis acid nature of PbI2, a key chemical for making MAPbI3 perovskite (and others) for in situ cross-linking of polystyrene (PS) chains in the precursor solution. The resulting PS–perovskite devices without any encapsulating layer show a stable structure in ambient conditions after >1000 h of continuous 1.0 sun (AM 1.5G) illumination in air (relative humidity of 40–50%) at 45 °C, while also showing a slightly improved device performance. The stability is the result of the direct specific interaction between the polymer and the perovskite that reduces ion migration, charge recombination, trap-state density, and dark currents and at the same time leads to improve mobility and carrier lifetime. The interaction between the polymer and PbI2 also improves the crystallization kinetics, leading to larger grain size in the perovskite films. The cumulative effect of these improvements makes the reported polymer–perovskite hybrids well suited for long-term device applications and presents a new avenue for making stable polymer–perovskite composites.