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Keywords:

  • acceptor-donor-acceptor;
  • small molecules;
  • central blocks;
  • coplanarity;
  • morphology

Abstract

A series of acceptor-donor-acceptor alternative small molecules were synthesized containing electron-donating central building moieties of phenothiazine, 2,7-carbazole and thieno[3,4-b]thiophene and electron-accepting moieties of tetrazine on both sides. The various conformations of the central blocks, with the coplanarity in an order of phenothiazine<2,7-carbazole<thieno[3,4-b]thiophene, have an obvious influence on the optical, electrochemical property and the crystallinity of small molecule. In addition, the blend films between small molecule and (6,6)-phenyl-C61-butyric acid methyl ester offered signi?cantly various morphologies, changing from uniform surface to interpenetrated networks. As a result, the bulk heterojunction photovoltaic devices based on the three small molecules provided varied performance, and the highest coplanar molecule based device exhibited the best photovoltaic performance.