Oxide-Polymer Heterojunction Diodes with a Nanoscopic Phase-Separated Insulating Layer.

Organic semiconductor-insulator blend films are widely explored for high-performance electronic devices enabled by unique phase separation and self-assembly phenomena at key device interfaces. Here we report the first demonstration of high-performance hybrid diodes based on p-n junctions formed by a p-type poly(3-hexylthiophene) (P3HT)-poly(methylmethacrylate) (PMMA) blend and n-type indium-gallium-zinc oxide (IGZO). The thin film morphology, microstructure, and vertical phase separation behavior of the P3HT films with varying contents of PMMA are systematically analyzed. Microstructural and charge transport evaluation indicates that the polymer insulator component positively impacts the morphology, molecular orientation, and effective conjugation length of the P3HT films, thereby enhancing the heterojunction performance. Furthermore, the data suggest that PMMA phase segregation creates a continuous nanoscopic interlayer between the P3HT and IGZO layers, playing an important role in enhancing diode performance. Thus, the diode based on an optimal P3HT-PMMA blend exhibits a remarkable 10-fold increase in forward current versus that of a neat P3HT diode, yielding an ideality factor value as low as 2.5, and a moderate effective barrier height with an excellent rectification ratio. These results offer a new approach to simplified manufacturing of low-cost, large-area organic electronics technologies.