Highly efficient polymer solar cells cast from non-halogenated xylene/anisaldehyde solution

• Published in: Energy & environmental science Vol. 8; no. 9; pp. 2744 - 2752
• Main Authors: Sprau, Christian, Buss, Felix, Wagner, Michael, Landerer, Dominik, Koppitz, Manuel, Schulz, Alexander, Bahro, Daniel, Schabel, Wilhelm, Scharfer, Philip, Colsmann, Alexander
• Format: Journal Article
• Language: English
• Published: 01.01.2015
• Subjects: Additives; Copolymers; Deposition; Devices; Fullerenes; Photovoltaic cells; Solar cells; Solvents
• ISSN: 1754-5692; 1754-5706
• DOI: 10.1039/c5ee01917f

Several high performance polymer:fullerene bulk-heterojunction photo-active layers, deposited from the non-halogenated solvents o -xylene or anisole in combination with the eco-compatible additive p -anisaldehyde, are investigated. The respective solar cells yield excellent power conversion efficiencies up to 9.5%, outperforming reference devices deposited from the commonly used halogenated chlorobenzene/1,8-diiodooctane solvent/additive combination. The impact of the processing solvent on the bulk-heterojunction properties is exemplified on solar cells comprising benzodithiophene-thienothiophene co-polymers and functionalized fullerenes (PTB7:PC 71 BM). The additive p -anisaldehyde improves film formation, enhances polymer order, reduces fullerene agglomeration and shows high volatility, thereby positively affecting layer deposition, improving charge carrier extraction and reducing drying time, the latter being crucial for future large area roll-to-roll device fabrication. Several high performance polymer:fullerene bulk-heterojunctions are deposited from non-halogenated xylene/anisaldehyde solution, yielding power conversion efficiencies up to 9.5%.