Modulating Interfacial Carrier Dynamics via Spatial Conformation toward Efficient and Stable Perovskite Solar Cells

Abstract Interfacial defects result in serious carrier nonradiative recombination. The correlation between spatial conformation of modifiers and interfacial carrier dynamics is scarcely revealed. Here, an effective interfacial carrier dynamics and defect passivation modulation strategy via controlling spatial conformation of modification molecules is reported. Two kinds of similar Lewis base ligand molecules, biuret (BU) and dithiobiuret (DTBU), are employed to modify the surface of perovskite films. BU and DTBU can effectively passivate interfacial defects but the former is more effective than the latter on account of higher electronegativity and more advantageous molecular spatial arrangement. The planar symmetrical BU molecules can arrange compactly and orderly on the surface of perovskite films while the adsorbed DTBU molecules with a twisted asymmetrical structure are relatively chaotic. BU modification reduces interfacial energy offset, ameliorates improved interfacial energy band alignment, and speeds up hole extraction. In contrast, a much thicker adsorbed layer is yielded after DTBU treatment, which impedes carrier extraction and transfer and accordingly leads to grievous nonradiative recombination. The spatial conformation difference produces an inverse influence on device performance (positive for BU and negative for DTBU). The power conversion efficiency is much enhanced from 21.66% to 23.54% after BU modification along with improved stability.