Anion-Induced Catalytic Reaction in a Solution-Processed Molybdenum Oxide for Efficient Inverted Ternary Organic Photovoltaics

Solution-processed transition metal oxides (TMOs) prepared from complex ion precursors are developed as promising scalable interfacial layers for non-fullerene organic photovoltaics (OPVs); however, challenges remain in achieving defect-free and highly oriented metal-oxygen networks without post-deposition treatments due to the presence of residual organic metal-binding ligands in films. Herein, the novel strategy that the problematic organic metal-binding ligands in TMO precursors can be successfully eliminated by an anion-induced catalytic reaction (ACR) at room temperature is demonstrated, in which the low-level anions induce electron redistribution and instability of TMO precursors, expediting binding ligand removal during the hydrolysis reaction. The subsequent condensation process facilitates a dimensionally confined and continuous metal-oxygen network with a 20-fold increase in electrical conductivity (from 8.4 x 10(-4) to 1.8 x 10(-2) S m(-1)) and superior work function tunability (from 5.1 to 5.3 eV) compared to the pristine film. The ACR-derived TMO thin film on top of a ternary PBDB-TF:Y6:PC71BM photoactive layer enables an inverted device configuration with improved efficiency of 17.6%, as well as enhanced stability over 70% of the initial efficiency for up to 100 h AM 1.5G illumination.

Automated summary

This study demonstrates a novel strategy of eliminating problematic organic metal-binding ligands in TMO precursors through an anion-induced catalytic reaction (ACR) at room temperature, promoting the formation of a metal-oxygen network. The ACR-derived TMO thin film on top of a photoactive layer shows excellent electrical conductivity and work function tunability, leading to higher efficiency and longer stability in inverted device configurations.