All-Polymer Solar Cells with Bulk Heterojunction Films Containing Electron-Accepting Triple Bond-Conjugated Perylene Diimide Polymer

Abstract

A triple bond-linked perylene diimide (PDI) conjugated polymer, poly{[N,N'-dioctylperylene-3,4,9,10-bis(dicarboximide)-1,7(6)-diyll-alt-[(2,5-bis(2-ethylhexyl)-1,4- phenylene)bis(ethyn-2,1-diyl]} (PDIC8-EB), was examined as an electron-accepting component in all-polymer solar cells. As an electron-donating component, poly[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyllthieno[3,4-b]-thiophenediyl] (PTB7) and poly[4,8-bis(5-(2-ethylhexyp thiophen-2-yl)benzo[1,2-b:4,5-b'] dithiophene-alt-3-fluorothieno [3,4-b]thiophene-2-carboxylate] (PTB7-Th) were introduced in order to investigate the feasibility of PDIC8-EB because of their similarity. Results showed that the power conversion efficiency (PCE) was higher for the PTB7-Th:PDIC8-EB solar cells (PCE = 3.58%) than the PTB7:PDIC8-EB solar cells (PCE = 2.81%). The better performance of the PTB7-Th:PDIC8-EB solar cells has been attributed to the formation of a well-defined nanodomain morphology in the PTB7Th:PDIC8-EB bulk heterojunction layer, as measured with transmission electron microscopy (TEM), atomic force microscopy (AFM), and synchrotron radiation grazing incidence X-ray diffraction (GIXD).