Over the past 20 years, organic compounds have increasingly found applications as active materials in devices such as computer displays or solar cells. Our group is currently synthesizing molecular materials for use in new-generation solar cells (e.g. bulk heterojunction solar cells, perovskite solar cells). Some important goals in this field include the preparation of fullerene or non-fullerene electron acceptors that can surpass the efficiency of the gold standard fullerene PC70BM, the synthesis of hole transporting materials that boost the efficiency of perovskite solar cells, and a supramolecular approach for achieving an interdigitated heterojunction solar cell. For a recent review article on new-generation solar cells click here.
Azafullerenes for Organic Solar Cells
At the outset of this project, we wondered why, prior to 2014, there were no reports of azafullerenes as electron acceptors in organic solar cells. Azafullerenes are a class of fullerenes in which one carbon atom is replaced by a nitrogen atom. We hypothesized that these compounds could potentially outperform benchmarks PC60BM and PC70BM in organic solar cells by having their light absorption further shifted toward the visible region of the spectrum.
To test this hypothesis, we synthesized a solution-processable, dodecyloxyphenyl substituted azafullerene monoadduct (DPC59N, see Image) and used it as electron acceptor in bulk heterojunction organic solar cells (in collaboration with Prof. Emilio Palomares, ICIQ Tarragona). Due to its relatively strong absorption of visible light, DPC59N did indeed outperform PC60BM in respect to short circuit current (JSC) and external quantum efficiency (EQE) in blends with polymeric donor P3HT.