An indigo-based polymer bearing thermocleavable side chains for n-type organic thin film transistors†
A new n-type semiconducting polymer based on indigo having thermocleavable tert-butoxycarbonyl (t-Boc) groups was synthesized and used as an active layer in organic thin film transistors (OTFTs). Twisting of the polymer main chain due to the presence of the bulky t-Boc groups renders this indigo-based polymer highly soluble. A post-deposition thermal treatment at a temperature above 170 °C could remove the t-Boc groups to retrieve the highly coplanar geometry of the unsubstituted indigo units. The thermally annealed polymer semiconductor films at 200 °C showed an electron mobility of up to ∼6 × 10−3 cm2 V−1 s−1 in OTFTs, which is a 5-fold increase compared to that of the indigo-based polymers reported previously due to the retrieved high backbone coplanarity.