The first Bulk Hetrojunction solar cells were developed in 1995 after observations of ultrafast charge transfer were made. The principle behind a BHJ is that there is a photo induced charge transfer between a mixture of two materials ( Donor and acceptor) with appropriate HOMO and LUMO levels. Charge transfer occurs only at the interfaces within the complex intertwining morphology created in a BHJ which limits efficiency. Controlling the morphology of the bulk Hetrojunction is key to the development of cheap and efficient organic solar cells. For this reason we have begun to develop a series of photo-cross linkable materials that can be spin coated as thin films with the aim of controlling the phase separated morphology of the BHJ through π stacking , H-bonding and sterics. We will particularly focus on squaraines and diketopyrrolopyrroles for the development of a BHJ with high degrees of internal order.
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