Molecular Regulation toward SAM/Perovskite Interface for Efficient p-i-n Perovskite Solar Cells

Perovskite solar cells with a typical layered structure, defects and unsatisfied energy band arrangement at the interfaces have significantly affected carrier extraction/transportation even device stability. Therefore, appropriate interface modification is essential for constructing efficient and stable devices. In this work, we designed two asymmetric SAM materials, LW-1 and LW-2, to regulate the bottom interface of inverted perovskite solar cells, including passivating the FTO/SAM buried interface and the bottom interface of perovskite films by their substituted groups (Cl⁻ and S²⁻). Typically, Cl⁻ substitution positions were found to have remarkable impact on dipole moment and interfacial properties, and detailed discussion about these effects has been carried out. More uniform perovskite grains and higher crystallinity on the LW-1 substrate were obtained, thus leading to lower trap densities of the perovskite bulk and the perovskite interface and higher charge collection efficiency (η_C). Consequently, LW-1 based devices exhibited 26.38% efficiency, outperforming corresponding LW-2 based devices. Moreover, LW-1 based devices exhibited steady-state output efficiency of 26.0% and maintained 90.9% of its original efficiency after 500 h MPP operational stability testing under 60 °C heating, continuous illumination from a white LED lamp and bias voltage close to the maximum power point voltages.