Recently Advanced Polymer Materials Containing Dithieno[3,2-b:2,3-d]phosphole Oxide for Efficient Charge Transfer in High-Performance Solar Cells

Two novel semiconducting polymers based on benzodithiophene and dithienophosphole oxide (DTP) units are designed and synthesized. A novel electron-deficient DTP moiety is developed. Surprisingly, the introduction of DTP units brings highly polarizable characteristics, which is beneficial for the photocurrent in solar cells. Thus, the donor-acceptor type of conjugated polymers based on this novel acceptor has superior charge transfer properties and highly efficient PL quenching efficiencies. As a result, polymer solar cells (PSCs) with high power conversion efficiencies of 6.10% and 7.08% are obtained from poly(3,5-didodecyl-4-phenylphospholo[3,2-b:4,5-b']dithiophene-4-oxide-alt-4,8-bis(5-decylthiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene) (PDTP-BDTT) and PDTP-4-oxide-alt-4,8-bis(5-decylselenophen-2-yl)benzo[1,2-b:4,5-b']dithiophene) (PDTP-BDTSe), respectively, when the photoactive layer is processed with the 1,8-octanedithiol (ODT) additive. The PDTP-BDTSe copolymer is now the best performing DTP-based material for PSCs. Using the polarizable unit strategy determined in this study for the molecular design of conjugated polymers is expected to greatly advance the development of organic electronic devices.