Collaborative Strategy of Multifunctional Groups in Trifluoroacetamide Achieving Efficient and Stable Perovskite Solar Cells

The additive strategy is considered to be an effective scheme to purposefully passivate defect sites in perovskite materials. Herein, a small molecule trifluoroacetamide (TFAA) with C═O, −NH 2 , and F groups is incorporated into the perovskite precursor solution to alleviate the defect densities of the perovskite material from the source, so as to obtain high‐quality FA 0.85 MA 0.15 PbI 3 perovskite absorber and its assembled photovoltaic devices. Thanks to the interactions of Lewis acid of C═O and undercoordinated Pb 2+ , N—H and I − via hydrogen bond, and F and FA + fragments, the nonradiative recombination sites are effectively inhibited, simultaneously promoting the nucleation and grain growth of perovskite. The analysis results demonstrate that the introduction of TFAA additive greatly enhances the crystal quality of bulk perovskite absorber, ameliorates the surface morphology of perovskite film, and improves the extraction and transfer abilities of photogenerated carriers from perovskite absorber. The perovskite solar cells (PSCs) based on TFAA agent yield a champion power conversion efficiency of 24.16%, 8.3% better than that of the control device (22.31%). More importantly, the modified perovskite film has good harsh humidity stability and the unpackaged PSCs maintain outstanding photovoltaic performance in atmospheric environment, thermal, and light conditions.