Defect Regulation of Efficient Dion-Jacobson Quasi-2D Perovskite Solar Cells via a Polyaspartic Acid Interlayer

Interfacial modification is a promising strategy to fabricatehighlyefficient perovskite solar cells (PSCs). Nevertheless, research studiesabout optimization for the performance of Dion-Jacobson (DJ)-phasequasi-2D PSCs by underlying surface modification are rarely reported.The relevant influence of interfacial modification on defect regulationin the bulk and at the interface for PSCs is still unexplored. Herein,an interlayer of polyaspartic acid (PASP) was introduced at the interfaceof a hole transporting layer and a perovskite absorber to regulateboth the film quality and interface property for BDA-based DJ quasi-2DPSCs (n = 5). The PASP interlayer suppressed thecharge recombination, restricted the interfacial charge accumulation,and promoted the charge transport in devices and therefore improvedthe power conversion efficiency of PSCs from 15.03 to 17.34%. Moreover,through device simulation, it was concluded that the increase of open-circuitvoltage (V (oc)) was mainly attributed tothe suppression of interface defects, while the increase of short-circuitcurrent (J (sc)) was ascribed to the restrictionof interface defects and perovskite bulk defects. The improvementof both V (oc) and J (sc) originated from the passivation of shallow defect states.The present work provides a promising route for the fabrication ofefficient quasi-2D PSCs and enriches the fundamental understandingof defect regulation on photovoltaic performance.