The Influence of Side-Chain Position on the Optoelectronic Properties of a Red-Emitting Conjugated Polymer

Abstract

A study of the organic semiconductor F8TBT is presented, directly comparing a conventional form (F8TBT-out) with a form with varied alkyl side-chain position (F8TBT-in), in terms of optical properties and device performance in light-emitting-diodes (LEDs). Computational simulations of the side-chain position with respect to the TBT unit reveal geometrical differences between F8TBT-out and F8TBT-in. π-π conjugation on the backbone of F8TBT-in is interrupted by a distortion of the benzothiadiazole ring, leading to a blue-shift of the absorption spectrum and increased photoluminescence quantum efficiency. Both conventional and hybrid LEDs demonstrate that devices with F8TBT-in show improved performance, as compared to F8TBT-out, illustrating how tuning the optoelectronic properties of conjugated polymers by varying the placement of side chains has an important role in device optimization. The optical and electrical properties of the organic semiconductor F8TBT are tailored by changing the position of the alkyl side chains. A conventional form of F8TBT (F8TBT-out) and a form with varied alkyl side-chain position, F8TBT-in, are directly compared in terms of optical properties and light-emitting-diode device performance. This illustrates how the placement of side chains has a very important role for device optimization.