Asymmetric Injection in Organic Transistors via Direct SAM Functionalization of Source and Drain Electrodes.

The fabrication of organic optoelectronic devices integrating asymmetric electrodes enables optimal charge injection/extraction at each individual metal/semiconductor interface. This is key for applications in devices such as solar cells, light-emitting transistors, photodetectors, inverters, and sensors. Here, we describe a new method for the asymmetric functionalization of gold electrodes with different thiolated molecules as a viable route to obtain two electrodes with drastically different work function values. The process involves an ad hoc design of electrode geometry and the use of a polymeric mask to protect one electrode during the first functionalization step. Photoelectron yield ambient spectroscopy and X-ray photoelectron spectrometry were used to characterize the energetic properties and the composition of the asymmetrically functionalized electrodes. Finally, we used poly(3-hexylthiophene)-based organic thin-film transistors to show that the asymmetric electronic response stems from the different electronic structures of the functionalized electrodes.