Wearable Tin‐Based Perovskite Solar Cells Achieved by a Crystallographic Size Effect

Tin-based perovskite solar cells (PSCs) demonstrate a potential application in wearable electronics due to its hypotoxicity. However, poor crystal quality is still the bottleneck for achieving high-performance flexible devices. In this work, graphite phase-C3N4 (g-C3N4) is applied into tin-based perovskite as a crystalline template, which delays crystallization via a size-effect and passivates defects simultaneously. The double hydrogen bond between g-C3N4 and formamidine cation can optimize lattice matching and passivation. Moreover, the two-dimensional network structure of g-C3N4 can fit on the crystals, resulting an enhanced hydrophobicity and oxidation resistance. Therefore, the flexible tin-based PSCs with g-C3N4 realize a stabilized power conversion efficiency (PCE) of 8.56 % with negligible hysteresis. In addition, the PSCs can maintain 91 % of the initial PCE after 1000 h under N2 environment and keep 92 % of their original PCE after 600 cycles at a curvature radius of 3 mm.