Sharply Increased Current in Asymmetrically Aligned Polycrystalline Polymer Transistors With Sub-Domain-Size Channels

Shortening channels to the feature length of polymer domains is important to understand the charge transport in semiconducting polymers from macroscopic to microscopic scales. In this work, we fabricated polymer transistors with sub-domain-size channels by electron-beam lithography and asymmetrically aligned domains by off-center spin coating, in which a dry self-patterning method with hexagonal boron nitride was developed to eliminate parasitic leakage. The current sharply increased by 60 times when the channel length was shortened from 200 to 80 nm. The device with an 80 nm-long channel in the direction parallel to the aligned polymer domains delivered a saturation current 160 times higher than that of the orthogonal counterpart. These results and a velocity calculation suggested that the bottleneck of charge transport in electronic devices is domain boundaries. These results highlight the importance of high-efficiency intra-domain charge transport and also the inter-domain limitation. Our findings will contribute to further polymer optimization to improve the performance of polymer devices.