Deuteration‐functionalized self‐assembled monolayers for <scp>UV</scp> ‐durable perovskite solar cells

Abstract Ultraviolet (UV) light‐induced degradation at the buried interface poses a significant challenge to the long‐term stability of perovskite solar cells (PSCs), resulting in substantial efficiency losses and hindering their commercialization. Here, we developed two simple deuterated self‐assembled monolayers (SAMs), 2DPh‐4PACz and 1DPh‐4PACz. In particular, 2DPh‐4PACz, featuring double deuterophenyl groups as π‐conjugated extension units, demonstrates enhanced intrinsic UV stability, improved hole‐extraction capability, and effective protection of the perovskite film against UV exposure, while simultaneously improving film quality. As a result, PSCs incorporating 2DPh‐4PACz achieved a power conversion efficiency (PCE) of 26.34% (certified 25.9%) and retained 96.9% of their initial PCE after 240 h of continuous UV irradiation, representing the best UV light stability reported to date. Additionally, extensive UV‐aging experiments were conducted comparing with Ph‐4PACz, confirming deuteration of SAMs as an effective strategy to improve UV resistivity. Moreover, these devices maintained 92.8% of their initial PCE after over 900 h of thermal aging at 85°C, and 73% after more than 1380 h at 80% relative humidity (RH). This deuterophenyl groups design strategy with π‐conjugated extension offers a promising molecular design route for next‐generation SAMs in high‐performance, durable PSCs. image