A high mobility conjugated polymer composed of a new fused selenophene building block for organic field effect transistors

Abstract

Substitution of atoms in the π-conjugated system is one of most common strategy to tune the properties of conjugated molecules in organic electronics. We synthesized a new conjugated polymer (PDSSTV) with fused-ring-structure, diselenoselenophene (DSS). The polymer was synthesized via stille polymerization in chlorobenzene under microwave heating. The optical band gap of PDSSTV measured 1.70 eV in both solution and film due to its pre-aggregated state even in solution using UV-Vis absorption spectroscopy. In density functional theory (DFT) analysis, PDSSTV showed a twisted conformation arising from the large size of Selenium in DSS. The crystallinity of the polymer was checked using GIXD analysis. Upon thermal annealing at 250℃, the intensity of the out of plane order diffraction peak was greatly improved and the crystalline coherence length was also increased in both (100) lamella d-spacing and (010) π-π stacking direction. The charge carrier mobility of PDSSTV was probed by fabricating organic field effect transistors with a top-gate/bottom contact (TG/BC) architecture to obtain 2 cm2 V-1 s-1 under relatively low operating voltage of -30 V.