Tin instead of aluminum as a back electrode in P3HT:PC71BM organic solar cells

Abstract

In the present work, a thin film of Sn metal, instead of aluminum, was deposited as a back electrode, using thermal evaporation, for fabricating organic solar cells composed of poly(3-hexylthiophene) and [6,6]-phenyl-C71 butyric acid methyl ester. The effect of post-thermal annealing on performance parameters of the solar cell was investigated at low temperatures (suitable for organic solar cells) up to 180 °C. In addition, the effect of thermal annealing on morphological (using scanning electron microscopy) and electrical properties (using a Hall effect setup) of the Sn thin films is reported and discussed here. The obtained minor effect of thermal annealing on the morphological and electrical properties of the Sn thin films is offset by an improvement in the performance parameters of the solar cells after post-annealing at 160 °C. The present study shows good electrical properties of Sn thin films which are comparable with those of aluminum thin films.