Donor–acceptor π-conjugated polymers based on terthiophene-3,4-dicarboxylate, dithienopyrrolobenzothiadiazole and thieno[3,4-c]pyrrole-4,6-dione units and their hole mobility

Abstract

We have synthesized three different p-type donor–acceptor π-conjugated polymers based on diethyl [2,2′:5′,2′′-terthiophene]-3′,4′-dicarboxylate, dithienopyrrolobenzothiadiazole and thieno[3,4-c]pyrrole-4,6-dione units. Chemical polymerization was carried using Suzuki and Stille coupling, and the obtained polymers were characterized by NMR, UV-vis, GPC and electrochemical techniques. Polymers PCBTTD, PTTPBT and PTPDPBT exhibited an optical bandgap of 2.1 eV, 2.1 eV and 1.9 eV, respectively. The measured hole mobility using the SCLC method for PCBTTD, PTTPBT and PTPDPBT was found to be 4.36 × 10⁻⁴ cm² V⁻¹ s⁻¹, 2.36 × 10⁻⁴ cm² V⁻¹ s⁻¹ and 2.18 × 10⁻⁴ cm² V⁻¹ s⁻¹, respectively. The hole mobility of PCBTTD was found to be higher due to the presence of the more electron rich carbazole unit in comparison with the DTPBT unit. The synthesized polymers exhibit decomposition temperatures above 200 °C, which demonstrates their good thermal stabilities for applications in optoelectronic applications. The obtained results show the great potential of these polymers as p-type polymer semiconductors.