Affiliation: | aAdvanced Technologies Development Laboratory, Matsushita Electric Works, Ltd., 1048 Kadoma, Osaka 571-8686, Japan bDepartment of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ, UK cExperimental Solid State Physics Group, Department of Physics, Imperial College London, London SW7 2BW, UK |
Abstract: | We present a study of dark air-exposure degradation of organic solar cells based on photoactive blends of the conjugated polymer, poly2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylene vinylene] (MDMO-PPV) with 6,6]-phenyl C61-butyric acid methyl ester (PCBM). Photovoltaic devices were fabricated on indium tin oxide (ITO) glass with or without a layer of poly (3,4-ethylenedioxythiophene):poly(4-styrene sulfonate) (PEDOT:PSS), and were studied without encapsulation. Photovoltaic performance characteristics were measured as a function of time for different ambient conditions (under white light irradiation and in the dark, and under air, dry oxygen and humid nitrogen atmospheres). It was found that a key cause of degradation under air exposure is light independent and results from water adsorption by the hygroscopic PEDOT:PSS layer. Measurements of the charge mobility and hole injection after air exposure showed that the degradation increases the resistance of the PEDOT:PSS/blend layer interface. |