Property-control of self-assembled monolayer by employing hydroscopic polyethylene glycol for efficient and stable p-i-n perovskite solar cells

Recent great achievements of p-i-n perovskite solar cells (PSCs) have been mainly fueled by the development and advancement of carbazole-based self-assembled monolayers (SAMs) used as the hole-transport layers (HTLs). Driven by the success of polar, hydroscopic polyethylene glycol (PEG) application in the perovskite and buffer layers, herein we have assessed how the incorporation of PEG as ADDITIVE and BILAYER influences the SAM HTL in PSCs. When PEG is used as ADDITIVE, the photovoltaic performance of PSCs is reduced. While, PSCs processed by BILAYER exhibit high power conversion efficiencies (PCEs) of 24.75% (lab-scale area: 0.039 cm 2 ) and 20.47% (large area: 1 cm 2 ), attributed to the beneficial features such as better film/morphology formation and minimizing interfacial recombination losses/defect densities. Furthermore, we also demonstrate outstanding 73% (after 1000 h, 25°C, in ambient air) and 74% (after 500 h, 85°C, in inert) PCE retentions for the unencapsulated devices, accounting for stronger interaction between the PEG and perovskite layers. Our study paves a facile way of the polymeric materials’ role played in the SAMs for improving the PCE and stability of PSCs through their surface modification.