| Increasing demand for renewable energy has resulted in a new interest for alternative technologies such as organic photovoltaics. With efficiencies exceeding 8% for both polymer and small molecule photovoltaics, organic photovoltaics are now being commercialized due to their flexibility and low weight which allow for their adoption in new applications such as portable electronics, smart fabrics, and building-integrated photovoltaics. To date, most research efforts have been focused on increasing power efficiency with little assessment of potential negative impacts associated with their large scale production. It is generally assumed that organic photovoltaics have low environmental impacts and are by nature inexpensive to produce since they are often solution processed. In the present work, a comprehensive analysis of the life cycle embodied energy for C60 and C70 fullerenes which are the most common acceptor molecules in organic photovoltaics, has been performed from cradle-to-gate, including the relative contributions from synthesis, separation, purification, and functionalization processes. The embodied energy of all fullerenes was calculated to be an order of magnitude higher than most bulk chemicals. These results have enabled the life cycle impact associated with the production of various types of organic photovoltaics to be calculated, including polymer, small molecule and multi-junction devices. An outcome of the life cycle assessment for organic photovoltaics shows that small molecule devices require significant fabrication energy from high vacuum processing and their efficiency is limited by poor absorption in the near-infrared (NIR). Therefore, a solution processing approach with novel NIR absorbing molecules in multi-junction devices has been developed in order to minimize the total cumulative energy. The combined efforts have led to the first demonstration of a spray-coated small molecule photovoltaic NIR device, using a combination of ZnPc and AlPc which is projected to have an embodied energy similar to single junction polymer devices. |
