Synergistic Interface Engineering with Quinoidal Thienoisoindigo and PDTON Achieves 23.7% Efficiency in Perovskite Solar Cells

Interfacial defects between the perovskite absorber and hole transport layer (HTL) remain a major bottleneck in the performance and stability of perovskite solar cells (PSCs). A synergistic interface engineering strategy is introduced, combining quinoidal small molecules-thienoisoindigo (TIIQ) and diketopyrrolopyrrole (DPPQ)-in the perovskite precursor solution, with the amphiphilic polymer PDTON incorporated via the antisolvent. This dual-functional approach significantly improves perovskite film quality by promoting larger grain growth, reducing trap densities, and enhancing charge transport. Fourier-transform infrared spectroscopy reveals a redshift in the cyano group absorption bands, confirming coordination between TIIQ/DPPQ and undercoordinated Pb²⁺ ions, enabling effective defect passivation. Among all configurations, the TIIQ-PDTON-treated film (T-PSK@PD) exhibits the highest crystallinity, smoothest morphology, and lowest recombination loss, delivering a champion power conversion efficiency (PCE) of 23.71% with 95% efficiency retention after 1920 h under ambient conditions. This study also marks the first successful application of high-performance n-type organic field-effect transistor materials as functional additives in lead-based PSCs. The multifunctional additive strategy offers a promising platform for addressing interfacial limitations, paving the way toward efficient and stable perovskite photovoltaics.