Cross-Linked Polymer Framework to Release Residual Strain of Perovskite Film by an Atomic Scale
Feihu Liu, Jie Dou, Wei Zhang, Yuchen Li, Yuhan Mei, Qiyao Guo, Qi Chen, Yuanyuan Zhao, Yingli Wang, Xinyu Zhang, Jialong Duan, Qunwei Tang
Abstract
The intrinsic thermally induced residual strain of formamidinium-based lead triiodide has been a great challenge for the instability. This intrinsic residual strain induces significant lattice distortion, particularly in the near-surface region of the perovskite active layer, while the mechanisms of stress regulation are still not well-understood. Here, we developed a photoinduced in situ polymerization strategy to alleviate the residual strain. The self-shrinkage behavior of polymers modulates the atomic-scale interactions within the perovskite lattice, effectively tuning its mechanical properties. Our study reveals the fundamental mechanisms underlying micro-to-macro mechanical property evolution. The cross-linked device exhibited reduced lattice distortion, achieving a power conversion efficiency of 25.56%. Additionally, the unencapsulated PSCs showed exceptional heat stability, retaining 90% of their initial efficiency even after 1000 h of exposure at 85 °C in an N 2 atmosphere. This polymer-based approach provides a promising platform for an in-depth investigation of gradient stress regulation in PSCs.