Peking University, Nov. 22, 2013: Organic thin film field-effect transistors show promising potential application in logical circuits, display and radio frequency identification (RFID) due to their low cost, light weight, flexibility and solution processability. Compared with small molecules, polymers show better solution processability, mechanical properties and thermodynamic stability. Among early conjugated polymers designed for polymer light-emitting diodes and bulk heterojunction solar cells, Poly(p-phenylene vinylene) (PPV)-based polymers attract the most interest. However, studies of their application in polymer field-effect transistors (PFET) are limited because of their relatively low hole mobilities (10-5 ~ 10-2 cm2 V-1 s-1).
Professor Pei Jian and Dr. Wang Jie-Yu’s group in College of Chemistry and Molecular Engineering (CCME), Peking University, carried out a series of studies about conjugated polymer materials for PFET based on novel PPV derivatives. They designed and synthesized a new type of PPV derivatives, benzodifurandione-based PPV, named BDPPV (BD is the abbreviation of Peking University, Beida ), to overcome problems in traditional PPV-based polymers. Through structure modification, including introducing electron-withdrawing groups to lower energy levels, forming hydrogen bonding to fix conformation and using farther branched alkyl chains developed by Pei and Wang’s group earlier to shorten π-π stacking distance, BDPPV based PFET devices realized electron mobilities as high as 1.1 cm2 V-1 s-1 under ambient conditions, four orders of magnitude higher than that of traditional PPV derivatives. Moreover, this is the first polymer that showed electron mobilities higher than 1 cm2 V-1 s-1 under ambient conditions. This research was published on Journal of American Chemical Society (J. Am. Chem. Soc.2013, 135, 12168) and was elected as cover paper. Meanwhile, their research was highlighted by this journal entitled as “New polymer derivative transports electrons faster than ever”.
Based on BDPPV, Pei and Wang’s group further developed donor-acceptor (D-A) polymers and found that D-A polymers showed electron mobilities as high as 1.7 cm2 V-1 s-1, while showed ambipolar transportation after exposure under ambient conditions, with improved hole mobilities of 0.45 cm2 V-1 s-1 and still high electron mobilities of 1.45 cm2 V-1 s-1. This result provides useful guidelines for simplifying the fabrication of logical circuits and was published on Advanced Materials (Adv. Mater. 2013, DOI: 10.1002/adma.201302278).
Based on recent research results, Pei and Wang’s group proposed the important influence of alkyl chains on device performance of organic semiconductors for the first time and was invited by American Chemical Society to write a perspective, named Roles of Flexible Chains in Organic Semiconducting Materials (Chem. Mater. 2013, DOI: 10.1021/cm4018776) for Celebrating Twenty-Five Years of Chemistry of Materials, which was elected as one of the cover papers. Their pioneering researches are of great significance in designing novel organic semiconductors and developing their applications.
Dr. Lei Ting from CCME, Peking University is the first author of all aboved papers. All the researches were supported by Ministry of Science and Technology of the People’s Republic of China (MOST), National Natural Science Foundation of China (NSFC) and Shanghai Synchrotron Radiation Facility (SSRF).
Source: College of Chemistry and Molecular Engineering
Edited by: Zhang Jiang