Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV16)
Publication date: 28th March 2016
Due to intensive research, the perfornance of organic solar cells has recently improved significantly and has crossed the 10% efficiency mark in the laboratory. For a broad application, further significant improvements are still needed. In this presentation, I will discuss recent work on small-molecule organic solar cells. One central research area is the design of suitable molecules which form the bulk heterojunction active layer, requiring a nanoscale phase separation and well-defined morphology to achieve efficient operation. A key challenge of the field is to find design rules which relate the molecular structure of absorber materials to layer morphology and cell properties. The difficulty is that small changes of the molecular structure, leaving the electronic properties of the individual molecule nearly unchanged, can lead to large changes in the crystal packing and molecular orientation, causing significant differences in the electronic properties in the active layer. Furthermore, I will discuss highly efficient tandem structures with optimized electrical and optical properties. Very efficient recombination contacts can be realized by n- and p-type doped transport layers. Structures based on these approaches have reached efficiencies of 12% and have the potential to reach approximately 20%. Furthermore, these high-efficiency cells also show already reasonable lifetimes. Finally, I will briefly discuss manufacturing aspects.