Selenium-containing core-expanded naphthalene diimides for high performance n-type organic semiconductors

摘要

The incorporation of heavy atoms into molecular backbone is an extremely straightforward strategy for fine-tuning the optoelectronic properties of organic semiconductors.However,it is rarely studied in n-type small molecules.Herein,by selenium substitution of NDI3 HU-DTYM2,two Se-decorated core-expanded naphthalene diimides(NDI)derivatives DTYM-NDI3 HUDSYM(1)and NDI3 HU-DSYM2(2)were synthesized.In comparison with the reference S-containing compound NDI3 HUDTYM2,the highest occupied molecular orbital(HOMO)and lowest unoccupied molecular orbital(LUMO)energy levels of 1 and 2 were fine-tuned with?HOMO of about 0.2 e V,?LUMO of 0.1 e V and the narrowed HOMO-LUMO gaps.More surprisingly,the as-spun organic thin film transistors(OTFTs)based on 1 and 2 both showedμe,satvalues as high as1.0 cm2 V-1 s-1,which are 2-fold higher than that of NDI3 HU-DTYM2 with the same device structure and measurement conditions.In addition,the single crystal OFET devices based on Se-containing compound NDI2 BO-DSYM2 showed a highμe,satvalue of 1.30 cm2 V-1 s-1.The molecular packing of NDI2 BO-DSYM2 in single crystals(two-dimensional supramolecular structure formed by intermolecular Se···Se interactions)is quite different from that of a S-containing compound NDI-DTYM2(one dimensional supramolecular structure formed by intermolecularπ-πstacking).Therefore,the Se substitution can cause dramatic change about molecular stacking model,giving rise to high n-type OTFT performance.Our results demonstrated an effective strategy of the heavy atom effect for designing novel organic semiconductors.