Self-Assembled Monolayer Dyes for Contact-Passivated and Stable Perovskite Solar Cells

Abstract

Surface modification of transparent conductive oxides (TCOs) with carbazole-based self-assembled monolayers (SAMs) is an effective method toward the formation of highly efficient hole-selective contacts, enabling the fabrication of high-performance perovskite solar cells (PSCs). However, the lack of long-term structural and performance stability of the TCO/SAM/perovskite stack endangers the market entry of PSCs. Here, it is demonstrated that these challenges can be overcome by employing dyes as multi-functional SAMs, simultaneously facilitating charge transport, passivating interfacial defects, and acting as a “molecular adhesive” layer, preserving structural integrity of the contact stack. Particularly, the surface modification of ITO with a dye (N719) monolayer is shown to create a hole-selective contact for the fabrication of p–i–n PSCs with power conversion efficiencies reaching 24%. The N719 SAM-based PSCs have also shown superior stability compared to state-of-the-art PSCs incorporating carbazole SAMs and polyarylamine hole-selective contacts by preserving ≈90% of their initial PCE under continuous light and thermal stress tests for 1000 h. The robustness of the ITO/N719/perovskite stack is attributed to its low interfacial trap density, UV resilience and strong adhesion capability. These findings place dye SAMs as a promising alternative for improving the performance of next-generation photovoltaics.