Improved Photovoltaic Performance of Inverted Two-Dimensional Perovskite Solar Cells via a Simple Molecular Bridge on...

NiO-based two-dimensional perovskite solar cells (2D-PSCs) have the advantages of low fabrication temperature, suitable energy level matching, suppressed hysteresis, and superior stability, while the poor interfacial contacts between NiO and perovskite layers limit the perovskite film growth and charge transfer. Herein, a simple molecule, urea, was used as a molecular modifier to form bifacial passivation on the buried interface of NiO/perovskite, resulting in better interfacial contact and efficient bifacial passivation. We demonstrated that efficient bifacial passivation mainly comes from strong interactions between urea and NiO or perovskite, which make urea a molecular bridge for smoother charge transfer. Moreover, urea can regulate the ratio of Ni³⁺/Ni²⁺, therefore boosting the conductivity of NiO, and adjust the morphology of the NiO film for better 2D-perovskite crystal growth. Besides, urea also passivates the bifacial defect states of both NiO and perovskite film, yielding reduced defect density of the perovskite film and superior charge transfer on the buried interface. Consequently, inverted 2D-PSCs with urea modification proved significant improvements in short-circuit current density and fill factor, resulting in improved power conversion efficiency from 14.64 to 16.84% with better stability in air.