Synergistic Dual-Site Coordination of a Multifunctional Phosphonate Additive for Efficient Perovskite Solar Cells

Abstract The accelerated evolutionary trajectory of perovskite solar cells has propelled them to the forefront as a preeminent candidate for affordable and efficient renewable energy technologies. However, crystal defects and bulk imperfections within the perovskite films critically undermine their photovoltaic performance, thereby hindering the commercialization. In this work, a multifunctional additive, diethyl (4-cyanobenzyl)phosphonate (D4CP), is incorporated into the perovskite precursor solution. Theoretical evidence reveals that D4CP forms robust coordination with Pb2+ ions via dual electron-donating pathways (P═O and C≡N bonds). Moreover, experimental outcomes reveal that the strategic incorporation of D4CP improves the crystallization quality and systematically passivates defects within the perovskite films, thereby mitigating defect-assisted recombination. Ultimately, the champion device incorporating D4CP achieves a peak PCE of 24.40%, outperforming the reference device (22.30%). The work positions D4CP as a transformative additive for perovskite solar cells that synergistically elevates PCE.