Improving polymer solar cell through efficient solar energy harvesting

In the last few years, several effective approaches have been developed to improve polymer solar cell performance. In this chapter, we summarized several of the efforts conducted in UCLA on polymer solar cells, of which each is associated to efficient light harvesting. We first discussed effective approaches to improve morphology and nanoscale structure control on the polymer active layer through (a) solvent annealing and (b) mixed solvent approaches, in order to enhance the crystallinity of polymer for enhancing absorption, charge transport, and efficiency in the RR-P3HT:PCBM system. Interface engineering work has led to the demonstration of novel inverted solar cell structure, which might have advantages over conventional device structure in solution electrode, transparent solar cell, and/or tandem structure. The third section is focused on the newly developed low bandgap polymers, which show 5.6% solar cell efficiency - a significant improvement over the model RR-P3HT:PCBM solar cell. The results are good representative of the recent progress in the field of organic solar cell.