Bulk heterojunction solar cell based on fullerene and polythiophene

Organic and polymer photovoltaic cells are becoming an extremely active research area to meet the urgent need for clean and renewable energy managements due to their potential applications as flexible, low cost and solution processable energy sources. The photophysics of such photoactive devices is based on the photo-induced charge transfer from donor-type semiconducting conjugated polymers to acceptor-type conjugated polymers or acceptor molecules such as buckminsterfullerene or C₆₀. At present, so-called bulk heterojunction structures based on blends of a polymeric donor of polythiophene and the soluble fullerene derivative [6,6]-phenyl C₆₁ butyric acid methyl ester (PCBM) as an acceptor component represent the material system with the highest power conversion efficiency reported to date (approximately 6.5%), and the regioregular head-to-tail polythiophene derivatives are still the most promising polymeric donor materials for such photovoltaic cells, as their efficient interchain π-stackings of the conjugated backbones allow for the optimum transport of positive charge carriers (holes) until now. The present review summarizes and analyzes the progress made about the bulk heterojunction solar cells based on fullerene and polythiophene at home and abroad in the past few years. Some issues to be addressed and hotspots to be further investigated are also presented and discussed.