Engineering stable p-type contacts towards efficient fully vacuum deposited perovskite solar cells

Abstract

Perovskite photovoltaics have recently achieved significant breakthroughs in cell efficiency, while offering simple and low-cost processability. Vacuum-based techniques are gaining increased attention due to their scalability and material versatility. However, fully vacuum-deposited devices remain rare, partly due to the limited availability of charge transport materials compatible with vacuum deposition. Additionally, sublimed organic contact materials often require high work function interlayers, such as MoO₃, or molecular oxidants, which complicate device stability. In this study we explore the use of simpler non-extended conjugated self-assembled monolayers (SAMs) as alternatives to these high work function interlayers, demonstrating improved hole extraction, higher fill factors, and enhanced long-term stability compared to state-of-the art vacuum-deposited architectures. As a proof of concept, devices incorporating SAMs/TaTm (N4,N4,N4′′,N4′′-tetra([1,1′-biphenyl]-4-yl)-[1,1′:4′,1′′-terphenyl]-4,4′′-diamine) interfaces and methylammonium lead iodide perovskite (MAPbI₃) achieve power conversion efficiencies exceeding 19.5%, approaching the highest reported values for fully evaporated stacks, along with remarkable thermal stability at 85 °C.