Perovskite Grain-Boundary Manipulation Using Room-Temperature Dynamic Self-Healing "Ligaments" for Developing Highly Stable Flexible Perovskite Solar Cells with 23.8% Efficiency.

Flexible perovskite solar cells (pero-SCs) are the best candidates to complement traditional silicon SCs in portable power applications. However, their mechanical, operational, and ambient stabilities are still unable to meet the practical demands, because of the natural brittleness, residual tensile strain, and high defect density along the perovskite grain boundaries. To overcome these issues, we carefully developed a crosslinkable monomer TA-NI with dynamic covalent disulfide bonds, H-bonds, and ammonium. The crosslinking act as "ligaments" attached on the perovskite grain boundaries. These "ligaments" consisting of elastomers and 1D perovskites, can not only passivate the grain boundaries and enhance moisture resistance but also release the residual tensile strain and mechanical stress in 3D perovskite films. More importantly, the elastomer can repair bending-induced mechanical cracks in the perovskite film because of dynamic self-healing characteristics. The resultant flexible pero-SCs exhibited promising improvements in efficiency, and record values (23.84% and 21.66%) were obtained for 0.062-cm 2 - and 1.004-cm 2 -devices; the flexible devices also showed overall improved stabilities with T 90 > 20000 bending cycles, operational stability with T 90 > 1248 h, and ambient stability (relative humidity = 30%) with T 90 > 3000 h. This strategy paves a new way for the industrial-scale development of high-performance flexible pero-SCs. This article is protected by copyright. All rights reserved.