Trap State Passivation By Rational Ligand Molecule Engineering Toward Efficient And Stable Perovskite Solar Cells Exceeding 23% Efficiency

The nonradiative recombination losses resulting from the trap states at the surface and grain boundaries directly hinder the further enhancement of power conversion efficiency (PCE) and stability of perovskite solar cells. Consequently, it is highly desirable to suppress nonradiative recombination through modulating perovskite crystallization and passivating the defects of perovskite films. Here, a simple and effective multifunctional additive engineering strategy is reported where 11 Maleimidoundecanoic acid (11MA) units with carbonyls (carboxyl and amide) and long hydrophobic alkyl chain are incorporated into a perovskite precursor solution. It is revealed that improved crystallinity, reduced trap state density, and inhibited ion migration are achieved, which is ascribed to the strong coordination interaction between the carbonyl groups at both sides of 11MA molecules and Pb2+. As a result, improved efficiency and stability are achieved simultaneously after introducing 11MA additive. The device with 11MA additive delivers a champion PCE of 23.34% with negligible hysteresis, which is significantly higher than the 18.24% of the control device. The modified device maintains around 91% of its initial PCE after aging under ambient conditions for 3000 h. This work provides a guide for developing multifunctional additive molecules for the purpose of simultaneous improvement of efficiency and stability.