Organic thin-film solar cells: next generation low-cost photovoltaic applications

Abstract

The growing concern about our environment and sustainable development focuses attention on renewable energy sources. One of these sources is the direct conversion of sunlight into electricity by means of photovoltaic cells. Solar energy has the potential to fulfil an important part of the sustainable energy demand for future power generations. Thereby, low-cost organic photovoltaic systems have come into the international research focus during the past couple of years. This report demonstrates external power conversion efficiencies of above 2.3% under AMI. 5 illumination (100 mW/cm²) and external quantum efficiency over 50% for organic thin-film photovoltaic cells using a phthalocyanine-fullerene (ZnPc/C₆₀) bulk heterojunction as an active layer, embedded into a p-i-n type architecture with doped wide-gap charge transport layers. The p-i-n architecture allows for the design of solar cells with high internal quantum efficiency where the photoactive region absorbs visible light and recombination losses at contacts are avoided. The current-voltage characteristics, power conversion efficiencies, the dependence of short circuit current on incident white light intensity, IPCE and the surface network  morphology of these films by atomic force microscope (AFM) are discussed.

Keywords: Organic semiconductors; Photovoltaics; Solar energy conversion.