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Published online by Cambridge University Press: 02 March 2011
In this study we investigate how exposure to ambient air and light during device processing affects the opto-electronic properties of poly-3-hexylthiophene (P3HT) : [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) bulk heterojunction solar cells (BHJ). The properties of pure P3HT layers prepared in an inert atmosphere, under ambient conditions, and additionally degraded under light in ambient conditions were investigated using photoluminescence (PL) and photoinduced absorption (PIA). It was observed that exposure to air during processing leads to oxygen doping of the polymer. Exposure to air combined with light was found to significantly decrease the PL and PIA signals. The current-voltage (I-V) and external quantum efficiency (EQE) characteristics of solar cells fabricated in an inert atmosphere were compared to solar cells processed under ambient conditions. It was observed that processing in air leads to a reduction in the photocurrent in the devices which is attributed to electron trapping by oxygen in the active layer.