Effect of temperature on the morphological and photovoltaic stability of bulk heterojunction polymer:fullerene solar cells

• Published in: Solar energy materials and solar cells Vol. 92; no. 7; pp. 753 - 760
• Main Authors: Bertho, Sabine, Janssen, Griet, Cleij, Thomas J., Conings, Bert, Moons, Wouter, Gadisa, Abay, D’Haen, Jan, Goovaerts, Etienne, Lutsen, Laurence, Manca, Jean, Vanderzande, Dirk
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2008
• Subjects: Glass transition temperature; Morphology; Organic photovoltaics; Thermal stability; Organic photovoltaics; Glass transition temperature; Morphology; Thermal stability
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2008.01.006

In high performance polymer:fullerene bulk heterojunction solar cells the nanoscale morphology of interpenetrating acceptor:donor materials is optimized through appropriate preparation conditions such as annealing and choice of solvent, but this initial state-of-the-art morphology will not remain stable during long-term operation. We report the effects of prolonged storage at elevated temperatures on both the morphology and the photovoltaic performance for the model systems MDMO-PPV:PCBM and P3HT:PCBM as compared to ‘High T g PPV’:PCBM based solar cells, where the ‘High T g PPV’ is characterized by its high glass transition temperature (138 °C). In situ monitoring of the photocurrent–voltage characteristics at elevated temperatures, in combination with a systematic transmission electron microscopy (TEM) study and complementary optical spectroscopy, reveals distinct degradation kinetics and morphological changes that indicate the occurrence of different underlying physico-chemical mechanisms.