Chalcogenopheno[3,2-b]pyrrole-Containing Donor–Acceptor–Donor Organic Semiconducting Small Molecules for Organic Field-Effect Transistors

Abstract

A group of chalcogenopheno[3,2-b]pyrroles, including thieno[3,2-b]pyrrole (TP), furo[3,2-b]pyrrole (FP), and selenopheno[3,2-b]pyrrole (SeP), and thieno[3,2-b]thiophene (TT) electron-donating units were coupled with a thiophene-flanked diketopyrrolo[3,4-c]pyrrole (ThDPP) acceptor to generate four donor–acceptor–donor (D-A-D) semiconducting small molecules (ThDPP-TT, ThDPP-FP, ThDPP-TP, and ThDPP-SeP). This study systematically investigated the differences between chalcogenopheno[3,2-b]pyrroles and TT. From the characterizations, chalcogenopheno[3,2-b]pyrrole-containing molecules showed lower band gaps and binding-energy cold crystallization behavior. The enthalpies of cold crystallization were correlated with the weight of the chalcogen in ThDPP-FP, ThDPP-TP, and ThDPP-SeP, which were evaluated as intermolecular chalcogen-bond interactions between chalcogen and pyrrole nitrogen in chalcogenopheno[3,2-b]pyrroles. A stronger chalcogen bond interaction resulted in stronger self-aggregation in thin films with thermal treatment, which resulted in a polycrystalline structure in chalcogenopheno[3,2-b]pyrrole-containing molecules. For the application in an organic field-effect transistor, all four molecules showed good performance with the highest hole mobilities as 6.33 × 10–3 cm2 V–1 s–1 for ThDPP-TT, 2.08 × 10–2 cm2 V–1 s–1 for ThDPP-FP, 1.87 × 10–2 cm2 V–1 s–1 for ThDPP-TP, and 6.32 × 10–3 cm2 V–1 s–1 for ThDPP-SeP, and the change of mobility is well correlated to the root-mean-square roughness of the thin films. Overall, all the chalcogenopheno[3,2-b]pyrrole-containing molecules showed lower band gaps, polymorphism, and better charge transport properties compared to TT-containing molecules, which motivates replacing TT with chalcogenopheno[3,2-b]pyrroles in conjugated polymers, non-fullerene small molecular acceptors, and narrow-band-gap donors.

Diselenophene‐Dithioalkylthiophene Based Quinoidal Small Molecules for Ambipolar Organic Field Effect Transistors

“…[ 49 , 50 ] Thus, selenophene has been extensively utilized in the development of p‐type OFETs with outstanding performance. [ 50 , 51 , 52 , 53 , 54 ] For example, by taking advantage of Se in the intramolecular lock series, the author's group has recently achieved significant advancements, with the selenotetradecyl‐substituted molecule DDTT‐SeBT exhibiting the highest hole mobility thus far reported for all/fused thiophene semiconductors (>4.0 cm 2 V −1 s −1 ). [ 55 ] Furthermore, chemical structures of the reported Se‐containing small molecules for OFETs have been given in Figure 1a,b .…”