The Influence of Structural Variations on the Heteroacenes Containing Dihydropyrrolo[3,2‐b]pyrrole Core on Their OFET Performances

Abstract

Heteroacenes containing a dihydropyrrolo[3,2‐b]pyrrole core such as 5,10‐dihydroindolo[3,2‐b]indole (DBPP) and dinaphtho [2,3‐b:2’,3’‐f]pyrrolo[3,2‐b]pyrrole(DNPP) are potential p‐type semiconductors for organic field‐effect transistors (OFETs) owing to their electron‐rich and easy‐to‐modify core structure. Here we report that how the structural variations such as ring fusion pattern, heteroatom introduction and chlorination influence the crystallinity, orientation and morphology of this type of heteroacenes hence their OFET performance. It is revealed that angular fused C8‐iso‐DNPP has a higher HOMO energy level with matches better with the work‐function of Au and shows better crystallinity and more uniformed morphology compared to the linearly fused isomer C8‐DNPP. Thus it exhibits very similar hole mobility to C8‐DNPP but much smaller threshold voltages. On the other hand, the introduction of extra N atoms into DNPP affords an analogue DQPP and greatly alters the orientation of the crystalline film from “edge‐on” to “face‐on”, which results in a two‐order decrease of the hole mobility. Our result also shows that heavily chlorinated DBPP (TClDBPP) leads to the completely loss of the hole transport capability due to the large π‐π distance imposed by the large chlorine atoms.