Recent Progress of Imide-functionalized N-type Polymer Semiconductors

Polymer semiconductors have attracted substantial interests in both academia and industry, recently, attributed to their distinctive advantages, including widely-tunable chemical structure and optoelectronic property, solution processability, and mechanical flexibility. In the last decade, a great deal of efforts have been dedicated to developing P-type (hole transporting) polymer semiconductors, however the development of N-type (electron transporting) polymer analogues lags far behind compared to their P-type counterparts due to the scarcity of highly electron-deficient building blocks, accompanied steric hindrance, and synthetic barriers. In fact, high-performance N-type polymer semiconductors are essential for organic complementary logic circuits and p-n junctions, hence it is imperative to develop high-performance N-type polymer semiconductors, which hinge on the design and synthesis of new electron deficient building blocks with compact geometry and good solubilizing capability. Among various electron deficient building blocks, imide-functionalized (hetero) arenes hold the most promising structural and electronic features for enabling N-type polymer semiconductors. This account summarizes the latest progress of N-type polymers, particularly the polymers based on imide-functionalized (hetero) arenes developed by our group. These new imide-functionalized (hetero) arenes include a series of ring-fused ladder-type heteroarenes up to 5 imide groups and 15 rings in a row, which offer a remarkable platform for developing N-type polymer semiconductors with widely tunable optoelectronic property and film morphology. In addition, a series of beta-position functionalized or modified bithiophene imide derivatives are also devised and synthesized. The introduction of the most electronegative fluorine atom and the substitution of thiophene with more electron deficient thiazole yield further lower-lying LUMO energy levels, which promote N-type characteristics for the polymer semiconductors in devices. This account introduces the materials design principles for N-type polymer semiconductors and elaborate the synthetic routes to the new imides and the corresponding polymer semiconductors. In addition, the N-type device performance of the polymer semiconductors based on these imidefunctionalized building blocks in organic field-effect transistors (OFETs) and polymer solar cells (PSCs) are commented, and the materials structure-property correlations are elaborated. Finally, our insights into future materials innovation of N-type polymer semiconductors by inventing new imide-functionalized building blocks are provided.

近年来,高分子半导体材料由于其可溶液化加工及柔性等特点,引起了学术界以及工业界的广泛关注.然而,相比于P-型高分子半导体,由于缺电子结构单元的缺乏、空间位阻效应及合成上的挑战,N-型高分子半导体材料的研究仍然相对较少,开发高性能的N-型高分子半导体仍然是有机电子领域面临的巨大挑战.本专论回顾了N-型高分子半导体材料的最新研究进展,重点介绍了我们课题组开发的酰亚胺基高分子半导体及其在有机场效应晶体管(OFETs)和有机太阳能电池(OPVs)中的应用.通过对分子结构设计以及相应的器件性能的总结,以期为高性能N-型高分子半导体材料的设计和开发提供进一步的指导和借鉴.