Effect of acceptor strength in new acceptor–donor–acceptor-type molecules on their miscibility with donor polymers for bulk-heterojunction fullerene-free solar cells. (November 2017)

• Record Type: Journal Article
• Authors: Park, Seo Yeon; Park, Gi Eun; Choi, Suna; Lee, Ji Hyung; Lee, Dae Hee; Cho, Min Ju; Choi, Dong Hoon
• Is Part Of: Dyes and pigments. Volume 146(2017)
• Page Start: 226
• Page End: 233
• Publication Date: 2017-11
• Subjects: Fullerene-free solar cells -- Spirobifluorene -- Accepting units -- Polarity -- Miscibility; Dyes and dyeing -- Periodicals; Pigments -- Periodicals; 667.2
• DOI: 10.1016/j.dyepig.2017.07.010
• Languages: English
• ISSNs: 0143-7208

Abstract

Abstract: We designed and synthesized two kinds of spirobifluorene (SP)-based acceptor–donor–acceptor (A–D–A)-type acceptor materials, denoted by SP-IC and SP-TCF, which have an A–D–A structure consisting of a 3D tetrathienospirobifluorene donor core and 2-(3-oxo-2, 3-dihydro-1 H -inden-1-ylidene)malononitrile (IC) or 2-(3-cyano-4, 5, 5-trimethylfuran-2(5 H )-ylidene)malononitrile (TCF) acceptors as terminal units, respectively. Their LUMO levels (−3.91 eV for SP-IC and −3.97 eV for SP-TCF) are suitable as n-type molecules for PTB7-Th-based polymer solar cells. However, their morphologies in blend films with a conjugated donor polymer, Poly([2, 6′-4, 8-di(5-ethylhexylthienyl)benzo[1, 2-b;3, 3-b]dithiophene]{3-fluoro-2[(2-ethylhexyl)carbonyl]thieno[3, 4-b]thiophenediyl}) (PTB7-Th), exhibited considerable differences. The PTB7-Th:SP-IC blend film exhibited a better-defined nanophase-separated morphology than PTB7-Th:SP-TCF blend film. The corresponding bulk heterojunction polymer solar cell based on PTB7-Th:SP-IC showed four times higher power conversion efficiency (PCE = 4.50%) than that of PTB7-Th:SP-TCF. The higher PCE was well explained by investigating the morphology, which was affected by the surface energy of the acceptor molecules at the donor–acceptor interface. Graphical abstract: Highlights: Two novel n-type 3D molecules were designed and synthesized. SP-IC and SP-TCF have amorphous nature and strong visible absorption. Morphology of blend films were significantly influenced by their surface energy. The polymer solar cell based on PTB7-Th:SP-IC showed high power conversion efficiency (PCE = 4.50%) due to good miscibility in blend film.