Dithieno[3,2-b:2′,3′-d]pyridin-5(4H)-one-based polymers with a bandgap up to 2.02 eV for high performance field-effect transistors and polymer solar cells with an open-circuit voltage up to 0.98 V and an efficiency up to 6.84%

Abstract

A new electron donor, 4-(2-octyldodecyl)-dithieno[3,2-b:2′,3′-d]pyridin-5(4H)-one (DTPO), for polymer semiconductors is reported. Its homopolymer PDTPO reveals a high hole mobility of 0.19 cm² V⁻¹ s⁻¹ in field-effect transistors. Its copolymers with benzodithiophenes (BDTO and BDTT), namely PDTPO-BDTO and PDTPO-BDTT, not only show wide optical bandgaps of 2.02 and 1.95 eV, but also possess deep HOMO levels of −5.38 and −5.44 eV, respectively. The polymer solar cell based on PDTPO-BDTO with an inverted architecture achieves a power conversion efficiency (PCE) of 6.84% with a high open-circuit voltage (V_oc) of 0.93 V, while the one with PDTPO-BDTT realizes the same PCE with conventional architecture and a reasonably high V_oc of 0.96 V. The PCEs are among the highest ever reported for wide bandgap PSCs. Compared to the blend with PDTPO-BDTO having the 2-ethylhexyloxy group, the one with PDTPO-BDTT having the 5-(2-ethylhexyl)thiophene-2yl- group is demonstrated to be superior as a result of faster exciton separation into free charge carriers and larger driving force for exciton dissociation, which results in high short-circuit current and V_oc, respectively. The wide optical bandgaps and the excellent device performances make these polymers good candidates for boosting the PCE of the PSCs with a ternary blend layer or tandem structures.