Synthetic Surface Design of Transparent Electrodes for Enhanced Molecular Contact in Perovskite Solar Cells

ABSTRACT Self‐assembled molecules (SAMs) as a molecular charge selective contact and interface with metal oxides are the new benchmark in p‐i‐n devices. Yet, transparent electrode (i.e., ITO) surface preparation is often performed with established protocols that do not exploit the full potential of self‐assembly. We introduce a simple, solution‐based ITO surface treatment strategy that enables improved contact formation by simultaneously tuning surface chemistry, conductivity and homogeneity. Contrary to the prevailing assumption that maximizing surface hydroxylation is the key for phosphonic‐acid‐based SAMs, we show that synthetic design with moderate hydroxyl and hydroxide content yields more uniform and electronically favourable interfaces for SAM anchoring. Electronically, the resulting contacts enable enhanced charge extraction, while offering improved layer homogeneity and operational stability. The treated interfaces further demonstrate improved resilience under extreme thermal cycling between −80°C and 80°C, relevant for low‐earth‐orbit (LEO) space operation. Importantly, we demonstrated the broad applicability of our approach across various materials, fabrication environments, and device structures, including single junction and tandem solar cells. These findings establish surface preparation as a design parameter on par with molecular engineering for robust perovskite optoelectronic devices.