Solution processable boron subphthalocyanine derivatives as active materials for organic photovoltaics

Here we present our work on development of new solution processable small molecules for efficient organic photovoltaic cells (OPVs). Boron subphthalocyanine derivatives possess unique structural and photophysical properties, i.e. excellent solubility, low tendency to aggregate, and high extinction coefficients, that enable the formation of high quality thin films via solution processing for OPVs application. Both p type (donor) and n type (acceptor) boron subphthalocyanine derivatives have been investigated. Using a soluble 2-Allylphenol SubPc derivative as donor and fullerene as acceptor, we have demonstrated simple planar heterojunction OPVs with power conversion efficiencies of over 1.7%, which represents one of the highest efficiencies for devices with solution processable small molecules to date. The use of fluorinated subphthalocyanines as acceptor and typical poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1, 4-phenylene vinylene] (MDMO-PPV) as donor has led to fully solution processed OPVs with efficiencies over 0.1%. Our work shows that solution processing of light harvesting small molecules has great potential for application in low cost thin film photovoltaic cells and boron subphthalocyanine derivatives are promising new-generation OPV materials.