In this Article, low-bandgap pTTDPP-BT polymers based on electron-accepting pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (DPP) and benzothiadiazole (BT) and electron-donating thienothiophene (TT) moieties were synthesized. Phototransistors have been fabricated using ambipolar-behaving pTTDPP-BT polymers as active channel materials. The electrical and photoresponsive properties of the pTTDPP-BT phototransistors were strongly dependent on the film annealing temperature. As-spun pTTDPP-BT phototransistors exhibited a low hole mobility of 0.007 cm2/(V·s) and a low electron mobility of 0.005 cm2/(V·s), which resulted in low photocurrent detection due to the limited transport of the charge carriers. Thermal treatment of the polymer thin films led to a significant enhancement in the carrier mobilities (hole and electron mobilities of 0.066 and 0.115 cm2/(V·s), respectively, for 200 °C annealing) and thus significantly improved photoresponsive properties. The 200 °C-annealed phototransistors showed a wide-range wavelength (405-850 nm) of photoresponse, and a high photocurrent/dark-current ratio of 150 with a fast photoswitching speed of less than 100 ms. This work demonstrates that a dual acceptor-containing low band gap polymer can be an important class of material in broadband photoresponsive transistors, and the crystallinity of the semiconducting polymer layer has a significant effect on the photoresponse characteristics.
Bibliographical noteFunding Information:
Financial support was provided by a grant (NRF-2015R1D1A1A01058493 and NRF-2017R1A2B2005790) from the Basic Science Program through the National Research Foundation (NRF) funded by the Ministry of Science, ICT and Future Planning a grant (NRF-2015M1A2A2056218) from the Technology Development Program to Solve Climate Changes of the NRF, and the New & Renewable Energy of the Korea Institute of Energy Technology Evaluation and Planning grant funded by the Korea Government Ministry of Knowledge Economy (KETEP 20163030013900).
© 2017 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Materials Science(all)