A dual-functional additive for crystallization regulated and defect passivated stable inverted perovskite solar cells

The main problems holding back inverted perovskite solar cells (PSCs) are poor crystal formation and too many defects inside the perovskite layer. We address both issues by introducing 4-aminobutylphosphonic acid, which effectively releases residual tensile stress and passivates film defects, leading to enhanced efficiency and stability. We report 4-aminobutylphosphonic acid as a multifunctional additive where the phosphonic acid (–PO3H2) and amine (–NH2) groups coordinatively passivate undercoordinated Pb2+ and I− vacancies, as supported by GIXRD measurements showing 64% reduction in residual tensile stress, and time-resolved photoluminescence shows enhanced carrier lifetime. The optimized devices achieve a champion power conversion efficiency (PCE) of 24.1% and retain 85% of its initial PCEs after 840 h under 1-sun illumination at 65 °C. This molecular engineering approach provides a facile route to concurrently boost efficiency and stability in inverted PSCs.