High Thermal Conductivity of Liquid Crystal Elastomer for Stress‐Less Flexible Perovskite Solar Cells

Abstract Flexible perovskite solar cells (FPSCs) have gained considerable attention for potential applications in portable and wearable electronics. However, the design principles governing FPSCs remain incompletely understood. In this study, two critical factors—thermal conductivity and elastic modulus—that significantly influence the thermal and mechanical stabilities of FPSCs are identified. Achieving stress‐less conditions is crucial for enhancing the performance of FPSCs. To address this, a liquid crystal elastomer (LCE) is employed as a buffer interlayer to effectively mitigate residual thermal stress. This is achieved by improving the thermal conductivity of the electron transport layer from 0.76 to 1.07 W mK −1 and softening the perovskite layer, reducing the Young's modulus from 50 to 42 GPa. The optimized thin films are utilized in both rigid and flexible PSCs, resulting in efficiencies of 24.5% and 22.8%, respectively. Remarkably, these devices demonstrated excellent thermal stability, with unpackaged LCE rigid PSCs retaining 85.6% of their initial efficiency after 504 h of aging at 85 °C. Moreover, robust mechanical stability in FPSCs is exhibited, with 88.4% of the original efficiency retained after 5400 bending cycles. This investigation elucidates the profound impact of thermal conductivity and Young's modulus on the efficiency and stability of flexible electronics.