Low-Band gap Conjugated Polymers with Strong Absorption in the Second Near-Infrared Region Based on Diketopyrrolopyrrole-Containing Quinoidal Units

Abstract

The development of low-band gap conjugated polymers with strong absorption in the second near-infrared (NIR-II) region is a big challenge because of the scarcity of an effective molecular design strategy. In the current paper, a series of conjugated polymers based on diketopyrrolopyrrole-containing quinoidal compounds have been synthesized and characterized. These polymers exhibited strong absorption in the NIR-II region with the absorption maxima above 1000 nm and optical band gaps as low as 0.84 eV. Owing to their strong near-infrared absorption, the polymers exhibited high photothermal conversion efficiencies of up to 53.1% upon 1064 nm laser irradiation (1 W cm–2). Top-gate and bottom-contact organic thin-film transistors (OTFTs) were fabricated to investigate their semiconducting properties. All the polymers showed ambipolar charge transport characteristics with reliable mobilities on the order of 10–1 cm2 V–1 s–1. Low optical band gaps, high photothermal conversion efficiencies, and good charge transport properties endow these polymers with great potential in organic electronics and bio-related applications.