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, like MoO3, or molecular oxidants, which complicate device stability. In this study we explore the use of simpler non-extended conjugated self-assemble 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 ºC.