Stabilizing Wide Bandgap Triple‐Halide Perovskite Alloy through Organic Gelators.

Engineering the chemical composition of metal‐halide perovskites via halide mixing allows a facile bandgap modulation but renders perovskite materials prone to photoinduced halide segregation. Triple‐halide alloys containing Cl, I, and Br were recently reported as a means to stabilize CsyFA1–yPb(BrxI1–x)3 perovskite under illumination. Herein, these triple‐halide alloys are found to be intrinsically less stable with respect to the reference I‐Br in ambient conditions. By exploiting the influence of low‐molecular‐weight organic gelators on the crystallization of the perovskite material, a triple‐halide alloy with improved moisture tolerance and thermal stability at temperatures as high as 120 °C is demonstrated. The hydroxyl‐terminated organic gelators are found to aggregate into nanoscale fibers and promote the gelation of the solvent inducing the formation of a 3D network, positively interfering with perovskite solidification. The addition of a tiny amount of organic gelators imparts a more compact morphology, higher crystallinity, and compositional stability to the resulting triple‐halide polycrystalline films, making them more robust over time without compromising the photovoltaic performance. Overall, this approach offers a solution toward fabrication of active perovskite materials with higher energy gap and improved stability, making these triple‐halide alloys truly exploitable in solar cells. [ABSTRACT FROM AUTHOR]