Achieving tunable work function in MoO_x thin films: A key to low-cost, high-performance organic electronics

MoO_x (Molybdenum oxide) thin films, as the interfacial modification layer of low-cost source-drain electrode materials, are considered the most promising material to solve electrical issues hindering the practical applications of organic thin-film transistors. However, precise control of the MoO_x work function remains a challenge for improving the electronic characteristics of organic thin-film transistors (OTFTs). In this work, we demonstrate universal strategies to achieve tunable work function of MoO_x thin films by adjusting O₂/(O₂+Ar) gas ratio during Mo deposition or by varying oxygen plasma treatment time on Mo thin films. The work function of MoO_x thin films increased from 4.85 eV to 5.80 eV by properly tuning O₂/(O₂+Ar) gas ratio. Moreover, as the oxygen treatment time increasing to 45 s, the work function of the MoO_x thin films undergoes an increase from 4.66 eV to 5.30 eV. The observed rise in work function is attributed to the formation of Mo atom higher oxidation states within the MoO_x thin films. Compared with non-plasma treatment OTFTs, the plasma-treated one shows excellent performance due to the ohmic contact between source-drain electrode and organic semiconductor interface layers. The present study is instructive for exploring interfacial modification layer materials with tunable work function, and manufacturing low-cost, high-performance and commercialized OTFT devices.