作者： Yong Li †, Tanmoy Dutta †, Nikolay Gerasimchuk §, Shijie Wu ∥, Kuldeep Shetye †, Lu Jin †, Ruixin Wang †, Da-Ming Zhu ‡, and Zhonghua Peng †

†Department of Chemistry and ‡Department of Physics, University of Missouri-Kansas City, Kansas City, Missouri 64110, United States

§ Department of Chemistry, Missouri State University, Springfield, Missouri 65897, United States

∥ Nano Scale Sciences Division, Keysight Technologies, Inc., Santa Clara, California 95051, United States

 

摘要：Charge carrier mobility and its optimization play a critical role in the development of cutting-edge organic electronic and optoelectronic devices. Even though space-charge-limited current (SCLC) hole mobilities as high as 1.4 cm2 V–1 s–1 have been reported for microscopically sized highly ordered liquid-crystalline conjugated small molecules, the SCLC hole mobility of device-sized thin films of conjugated polymers is still much lower, ranging from 10–6 to 10–3 cm2 V–1 s–1. Herein, we report the synthesis, characterizations, and thin-film SCLC mobility of three discotic conjugated polymers, INDT-TT, INDT-BT, and INDT-NDT. Optical studies indicate that polymer INDT-NDT adopts a folded conformation in solutions of good or poor solvents, whereas polymer INDT-TT stays as random monomeric chains in good solvents and interchain aggregates in poor solvents. INDT-BT polymer chains, however, stay as foldamers in dilute solutions of good solvents but interchain aggregates in concentrated solutions or poor solvents. Circular dichroism spectroscopy provides clear evidence for the helical folding of INDT-NDT in solutions. Thin films spin-coated from 1,2-dichlorobenzene solutions of the polymers show SCLC hole mobility of 2.20 × 10–6, 8.79 × 10–5, and 2.77 × 10–2 cm2 V–1 s–1 for INDT-TT, INDT-BT, and INDT-NDT, respectively. HRTEM and powder XRD measurements show that INDT-NDT pristine thin films contain nanocrystalline domains, whereas the INDT-TT and INDT-BT films are amorphous. Thin films of INDT-NDT:PC71BM blends show increased crystallinity and further improved SCLC hole mobility up to 1.29 × 10–1 cm2 V–1 s–1, one of the highest SCLC mobility values ever recorded on solution-processed organic semiconducting thin films. The persistent folding conformation of INDT-NDT is believed to be responsible for the high crystallinity of its thin films and its high SCLC mobilities.

 

關(guān)鍵詞：conjugated polymers; conjugated foldamers; circular dichroism; helical bias; hole mobility; space-charge-limited current