Improving Contact and Passivation of Buried Interface for High-Efficiency and Large-Area Inverted Perovskite Solar Cells

Inverted-structured perovskite solar cells (PSCs) mostly employ poly-triarylamines (PTAAs) as hole-transporting materials (HTMs), which generally result in low-quality buried interface due to their hydrophobic nature, shallow HOMO levels, and absence of passivation groups. Herein, the authors molecularly engineer the structure of PTAA via removing alkyl groups and incorporating a multifunctional pyridine unit, which not only regulates energy levels and surface wettability, but also passivates interfacial trap-states, thus addressing above-mentioned issues simultaneously. By altering the linking-site on pyridine unit from ortho- (o-PY) to meta- (m-PY) and para-position (p-PY), they observed a gradually improved hydrophilicity and passivation efficacy, mainly owing to increased exposure of the pyridine-nitrogen as well as its lone electron pair, which enhances the contact and interactions with perovskite. The open-circuit voltage and power conversion efficiency (PCE) of inverted-structured PSCs based on these HTMs increased with the same trend. Consequently, the optimal p-PY as HTM enables facile deposition of uniform perovskite films without complicated interlayer optimizations, delivering a remarkably high PCE exceeding 22% (0.09 cm(2)). Moreover, when enlarging device area tenfold, a comparable PCE of over 20% (1 cm(2)) can be obtained. These results are among the highest efficiencies for inverted PSCs, demonstrating the high potential of p-PY for future applications.