Naphthacenodithiophene Based Polymers—New Members of the Acenodithiophene Family Exhibiting High Mobility and Power Conversion Efficiency. (18th August 2016) - Knall, Astrid‐Caroline
Abstract : Wide‐bandgap conjugated polymers with a linear naphthacenodithiophene (NDT) donor unit are herein reported along with their performance in both transistor and solar cell devices. The monomer is synthesized starting from 2, 6‐dihydroxynaphthalene with a double Fries rearrangement as the key step. By copolymerization with 2, 1, 3‐benzothiadiazole (BT) via a palladium‐catalyzed Suzuki coupling reaction, NDT‐BT co‐polymers with high molecular weights and narrow polydispersities are afforded. These novel wide‐bandgap polymers are evaluated as the semiconducting polymer in both organic field effect transistor and organic photovoltaic applications. The synthesized polymers reveal an optical bandgap in the range of 1.8 eV with an electron affinity of 3.6 eV which provides sufficient energy offset for electron transfer to PC70 BM acceptors. In organic field effect transistors, the synthesized polymers demonstrate high hole mobilities of around 0.4 cm 2 V –1 s –1 . By using a blend of NDT‐BT with PC70 BM as absorber layer in organic bulk heterojunction solar cells, power conversion efficiencies of 7.5% are obtained. This value is among the highest obtained for polymers with a wider bandgap (larger than 1.7 eV), making this polymer also interesting for application in tandem or multijunction solar cells. Abstract : Naphthacenodithiophene‐benzothiadiazole (NDT‐BT) copolymers have been synthesized via a palladium‐catalyzed Suzuki coupling reaction. Compared to the analogous indacenodithiophene polymers, these NDT‐BT copolymers have a wider bandgap of 1.8 eV. Hole mobilities of around 0.4 cm 2 V –1 s –1 are observed and, in combination with a PC70 BM acceptor, power conversion efficiencies of 7.5% are obtained in organic bulk heterojunction solar cells.