High-Throughput Multiparametric Screening of Solution Processed Bulk Heterojunction Solar Cells

One of the major bottlenecks in the development of organic photovoltaics is the time needed to evaluate each material system. This time ranges from weeks to months if different variables such as blend composition, thickness, annealing, and additives are to be explored. In this study, the use of lateral gradients is proposed in order to evaluate the photovoltaic potential of a material system up to 50 times faster. A platform that combines blade coating using controllable velocity profiles (thickness gradients) with multichannel dispensers (composition gradients) and controlled lateral annealing variations (nanostructure gradients) is introduced. These samples are then analyzed using photocurrent and Raman imaging in order to correlate one to one the device performance, thickness, composition, and annealing temperature. The strength of the developed technology is shown by optimizing three different systems, namely PCDTBT:PC70BM, PTB7-Th:PC70BM, and PffBT4T-2OD:PC70BM, obtaining efficiencies approximate to 5%, 8%, and 9.5%, respectively, using less than 10 mg of each polymer in the process.