Optimized phase separation in low-bandgap polymer:fullerene bulk heterojunction solar cells with criteria of solvent additives. (December 2016)

• Record Type: Journal Article
• Authors: Choi, Youna; Kim, Geunjin; Kim, Heejoo; Lee, Seoung Ho; Kwon, Sooncheol; Kim, Junghwan; Lee, Kwanghee
• Is Part Of: Nano energy. Volume 30(2016:Dec.)
• Page Start: 200
• Page End: 207
• Publication Date: 2016-12
• Subjects: Bulk heterojunction solar cells -- Solvent additives -- Low-band gap polymer -- Phase separation; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2016.10.012
• Languages: English
• ISSNs: 2211-2855

Abstract

Abstract: We investigate a correlation between the type of solvent additives (SAs) with specific criteria such as aromatic additives (AAs) and non-aromatic additives (NAAs) and phase separation in the bulk heterojunction (BHJ) films comprising low-band gap polymer and fullerene derivatives. When AAs are used as SAs, the geometrical structures (π-π and lamellar stacking) of aggregated polymer chains do not significantly change. However, NAAs increase the lamellar stacking distance through a strong interaction with non-aromatic segments of polymers. Therefore, a well-phase separated BHJ morphology with the finer fibrils is developed, thereby leading to balanced charge mobilities and a reduced charge recombination in BHJ solar cells. Finally, the optimized solar cell exhibits a high power conversion efficiency of 7.9%. Graphical abstract: The correlation between the type of solvent additives with specific criteria such as aromatic additives (AAs) and non-aromatic additives (NAAs) and phase separation in the bulk heterojunction (BHJ) films is investigated. By strong interaction between NAAs and non-aromatic segment of polymers, a well-phase separated BHJ morphology with the finer fibrils is developed, thereby leading to balanced charge mobilities and a reduced charge recombination in BHJ solar cells. Highlights: We investigated the correlation between the phase separation in BHJ films and SA types with specific criteria (AAs and NAAs). A well-phase separated nano-morphology with balanced charge mobilities was obtained in the BHJ films processed with NAAs. This result would be helpful in determining suitable SAs for newly synthesized π-CP systems.