Carboxymethyl-Based Ionic Liquid Engineering for Efficient and Stable Inverted Perovskite Solar Cells

Perovskite solar cells (PSCs) have garnered significant attention due to their tunable bandgap, superior charge carrier properties, and easy fabrication processes, making them highly efficient energy conversion devices. Despite these advantages, nonradiative recombination due to defects in the perovskite layer continues to limit performance. This study addresses this issue by introducing 1-CarboxyMethyl-3-MethylImidazolium chloride (ImAcCl) into precursor solution to enhance film quality and suppress defect-induced recombination. The carboxylate groups (CO) and hydrogen donors (NH) in ImAcCl form coordination and hydrogen bonds, helping to reduce defect density of the perovskite film. Additive ImAcCl improves crystallinity, reduces surface roughness, and enhances charge carrier transport, leading to higher photovoltaic performance. With the ImAcCl additive, the power conversion efficiency and short-circuit current of PSCs significantly improve by 23.92% and 25.35 mA cm⁻², with a notable reduction in nonradiative recombination losses. This study highlights the significant potential of ImAcCl as an effective additive for defect passivation in PSCs, offering a promising pathway toward further efficiency improvements in next-generation solar cells.