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

A triple bond-linked perylene diimide (PDI) conjugated polymer, poly­{[<i>N</i>,<i>N</i>′-dioctylperylene-3,4,9,10-bis­(dicarboximide)-1,7­(6)-diyl]-<i>alt</i>-[(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)­carbonyl]­thieno­[3,4-<i>b</i>]-thio­phenediyl] (PTB7) and poly­[4,8-bis­(5-(2-ethylhexyl)­thiophen-2-yl)­benzo­[1,2-b:4,5-b′]­dithiophene-<i>alt</i>-3-fluorothieno­[3,4-<i>b</i>]­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 PTB7-Th: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)