The Dual Effect of Spatially Symmetric Polymer for Flexible Perovskite Solar Cells with Mechanical Robustness and Stability.

The successful commercialization of flexible perovskite solar cells (FPSCs) hinges on their long-term stability and scalability. Surface defects and residual stress stand out as the main factors impeding their performance. These elements play a substantial role in causing perovskite instability, which not only undermines the efficiency of FPSCs but also expedites device degradation. In this research, for the first time, aminopropyl double-ended polydimethylsiloxane (AP-PDMS) is employed to passivate the surface of perovskite films. The AP-PDMS spatial symmetric part like "pincers" captures two Pb and forms a hydrogen bond with FA, thereby effectively relieving the residual stress. Moreover, the hydrophobic siloxane within AP-PDMS acts as a protective barrier, preventing water from penetrating the perovskite. This approach yields high-quality perovskite films characterized by large grain sizes, low defect densities, and excellent crystallinity. Consequently, the enhanced device exhibits excellent moisture resistance stability. The FPSCs obtained a champion power conversion efficiency of 23.32%. More importantly, these FPSCs show the mechanical robustness with > 10,000 bending cycles (bending radius of 5 mm) and operational stability with > 1000 h.