Multilayer OPV cell achieves record efficiency

While fullerenes are the dominant acceptor materials in current OPV cells, the small absorption overlap with the solar spectrum tends to limit photocurrent generation. What's more, their deep energy level for electron conduction limits the open circuit voltage. Looking to overcome these limitations, the imec team decided to implement two fullerene-free materials in their OPV cell to see if this would yield similar or better results. They also used a simple three-layer stack instead of complex tandem architectures to improve the spectral responsivity range. The resulting OPV cell, which comprises two fullerene-free acceptors and a donor, arranged as discrete heterojunctions, has been shown to exhibit a quantum efficiency above 75% between 400 and 720nm. With an open circuit voltage close to 1V, the researchers achieved a power conversion efficiency of 8.4% - the highest yet reported.