Affording Balanced Ambipolar Transport by Solution-Processing Highly-Oriented and Bicontinuous Phase Structures

Ambipolar organic field-effect transistors (OFETs), capable of conducting both holes and electrons, offer significant potential for simplifying circuit design and manufacturing. However, solution-processed p-n blend films often suffer from molecular-level interference, which impedes efficient charge transport. In this work, we propose a method to fabricate p-n blending layer with a highly oriented and bicontinuous phase structure by incorporating a polymer into the blend solution. The vertical phase separation between small molecules and polymer was induced by the difference in their surface energy. The p-n blend layer on the top of polymer layer undergoes microphase separation, which forms an interpenetrating bicontinuous network with oriented striplike domains, thereby providing well-defined and independent transport pathways for both carrier types. Optimized OFETs exhibit excellent and balanced ambipolar mobilities in two blend systems, around 0.2 cm²V^-1s^-1 for holes and electrons in 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT): N,N'-bis(n-hexyl) naphthalene-1,4,5,8-tetracarboxylic acid diimide (NDI-C6) blend. Therefore, the study provides an effective, low-cost strategy to construct high-performance ambipolar OFETs via solution processing.