Molecular integration of Lewis bases for efficient and stable inverted perovskite solar cells

Abstract

The deliberate design of functional molecules holds substantial significance to passivate detrimental defects and enable fabrication of high-performance perovskite solar cells (PSCs). Nevertheless, a facile yet rigid approach for the systematic design and judicious selection of passivators remains to be established. In this study, we put forward a molecular integration strategy to identify a novel Lewis base molecule, namely dimethyl acetonylphosphonate (DMAPA), which incorporates the functional groups of previously reported Lewis base molecules of acetone (ACT) and trimethyl phosphate (TP). Theoretical computations demonstrate that the DMAPA molecule manifests a more advantageous interaction with perovskite crystals in comparison to ACT and TP ligands. Experimentally, the DMAPA molecule has been observed to surpass ACT and TP molecules in terms of mitigating trap densities and obtaining excellent device performance. These findings clearly substantiate the effectiveness of the molecular integration strategy. Concurrently, in situ characterization studies have elucidated that the DMAPA molecule can modulate the crystallization dynamics of halide perovskites and expedite the transformation of the intermediate phase into the perovskite black phase. Ultimately, the DMAPA-based p–i–n structured PSCs deliver a champion power conversion efficiency (PCE) of 25.59%, as well as remarkable stability. The unencapsulated cells retain over 85% of their initial performance after 1600 hours of annealing at 65 °C or 850 hours of operation under one-sun equivalent light illumination at the maximum power point (MPP) voltage. This work presents a simple yet effective methodology that effectively enriches the range of passivators, addressing the prevailing challenges associated with defect passivation in PSCs and advancing the field of perovskite technology.