NiO_x-Seeded Self-Assembled Monolayers as Highly Hole-Selective Passivating Contacts for Efficient Inverted Perovskite Solar Cells

摘要

Self-assembled monolayers (SAMs) have emerged as effective carrier transportlayers in perovskite (PVK) solar cells because of their unique ability to manipulateinterfacial property, as well as simple processing and scalable fabrication.However, the defects and pinholes derived from their sensitive adsorptionprocess inevitably deteriorate the final device performance. Herein, a sputterednickel oxide (NiO_x) interlayer is used as a seed layer to promote the adsorption ofthe [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz) SAMon the indium tin oxide (ITO) substrate. The promoted adsorption is attributed tothe enhanced tridentate binding between MeO-2PACz and NiO_x relative to theconventional bidentate binding between MeO-2PACz and ITO. In addition, theNiO_x modification can simultaneously improve the passivation ability and holeselectivityof the MeO-2PACz, provide a favorable energy-level alignment at theITO/PVK interface, and prevent a direct contact between PVK and ITO. As aconsequence, this NiO_x-seeded MeO-2PACz hole transport layer enables asignificantly enhanced power conversion efficiency of 19.9% in comparison with18.4% of the control device. This work provides an effective strategy to improvethe performance of the SAM-based photoelectric device.