Precise Patterning of Laterally Stacked Organic Microbelt Heterojunction Arrays by Surface-Energy-Controlled Stepwise Crystallization for Ambipolar Organic Field-Effect Transistors
Xiujuan Zhang, Jian Mao, Wei Deng, Xiuzhen Xu, Liming Huang, Xiaohong Zhang, Shuit-Tong Lee, and Jiansheng Jie*
Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou, Jiangsu 215123, P. R. China
Ambipolar organic field-effect transistors (OFETs) combining single-crystalline p- and n-type organic micro/nanocrystals have demonstrated superior performance to their amorphous or polycrystalline thin-film counterparts. However, large-area alignment and precise patterning of organic micro/nanocrystals for ambipolar OFETs remain challenges. Here, a surface-energy-controlled stepwise crystallization (SECSC) method is reported for large-scale, aligned, and precise patterning of single-crystalline laterally stacked p–n heterojunction microbelt (MB) arrays. In this method, the p- and n-type organic crystals are precipitated via a stepwise process: first, the lateral sides of prepatterned photoresist stripes provide high-surface-energy sites to guide the aligned growth of p-type organic crystals. Next, the formed p-type crystals serve as new high-surface-energy positions to induce the crystallization of n-type organic molecules at their sides, thus leading to the formation of laterally stacked p–n microbelts. Ambipolar OFETs based on the p–n heterojunction MB arrays exhibit balanced hole and electron mobilities of 0.32 and 0.43 cm2 V−1 s−1, respectively, enabling the fabrication of complementary-like inverters with large voltage gains. This work paves the way toward rational design and construction of single-crystalline organic p–n heterojunction arrays for high-performance organic, integrated circuits.