Improved performance in n-channel organic thin film transistors by nanoscale interface modification

We demonstrate that the electrical properties of n-channel thin film transistors can be enhanced by inserting a nanoscale interfacial layer, namely, cesium carbonate (Cs2CO3), between organic semiconductor and source/drain electrodes. Devices with the Cs2CO3/Al electrode showed a reduction of contact resistance, not only with respect to Al, but also compared to Ca. The improvement is attributed to the reduction in the energy barrier of electron injection and the prevention of unfavorable chemical interaction between the organic layer and the metal electrode. High field-effect mobility of 0.045 cm2/V s and on/off current ratios of 106 were obtained in the [6,6]-phenyl C60 butyric acid methyl ester-based organic thin film transistors using the Cs2CO3/Al electrodes at a gate bias of 40 V.