Crystallization control via ligand-perovskite coordination for high-performance flexible perovskite solar cells

Flexible perovskite solar cells (F-PSCs) have shown significant promise owing to their flexibility and high specific power density; however, their performance is frequently hampered by suboptimal perovskite crystallization at low temperatures. Herein, we introduce diammonium ligands with various electronegative heteroatoms to optimize perovskite crystallization on flexible substrates. Ligand-perovskite coordination effects reduce nucleation sites and extend the crystal growth duration by forming intermediate complexes. The enhanced coordination via ligand tailoring results in a wider window for crystal growth, subsequently decreasing trap density, mitigating residual strain, improving energetic alignment, and suppressing nonradiative recombination in films. The optimized F-PSCs exhibit impressive power conversion efficiencies of 24.47% on a 0.09 cm2 scale, 23.16% on a 1.0 cm2 scale, and 17.21% on a larger 19.8 cm2 scale. Furthermore, we demonstrate the potential of these cells to power autonomous systems in intelligent traffic applications. Our study not only sheds light on the impact of molecular coordination on perovskite crystallization dynamics during low-temperature processing, but also provides strategic guidance for growth optimization to achieve high-performance, scalable flexible perovskite photovoltaics.