Synthesis and application of dithieno[3,2-b:2′,3′-d]thiophene conjugated copolymer for organic field effect transistors and nitrogen dioxide sensors

Abstract

In order to achieve high-performance gas sensors based on polymer field-effect transistors (FETs) for detecting super-low concentrations of NO₂ gas, a novel copolymer poly(2,6-bis(3-dodecylthio-2-thienyl)-dithieno[3,2-b:2′,3′-d]thiophene) (PDTT-TTSC12) was synthesized through direct arylation polycondensation by using the palladium-catalyzed C–H activation with the unsubstituted dithieno[3,2-b:2′,3′-d]thiophene and dibrominated 4,4-bis(dodecylmercapto)- 2,2-bidithiophene as polymerization precursors. The polymer PDTT-TTSC12 was used to construct OFETs by solution method and exhibits p-type characteristics with the hole mobility of 6.4 × 10⁻³ cm ²V⁻¹s⁻¹. The polymer-based OFETs were further used to detect the NO₂, and the sensors show strong sensing response and excellent selectivity for NO₂, with the ratio of current change (ΔI/I₀ (%)) as high as 57 % to 1000 ppb NO₂. And the ΔI/I₀ (%) can still maintain at 2.54 % and the relative sensitivity (RS) value reaches as high as 254 % ppm⁻¹ when the gas concentration drops to 10 ppb, which demonstrates that the limit of detection for NO₂ can be improved to ppb level by low-cost polymer-based OFETs.