Transfer of Triplet Excitons in SingletFission-Silicon Solar Cells: Experiment and Theory Towards Breaking the Detailed-Balance Efficiency Limit

The power of the sun can be harvested with a solar cell, and much effort has been put into making this process more efficient. This thesis is about a novel type of solar cell that has a higher theoretical efficiency, the Singlet Fission-silicon solar cell. This new type of solar cell can use the energy in the different colors of the light more efficiently. The Singlet Fission layer absorbs light with a high energy and splits the energy into smaller energy packets, that are then transferred into a silicon solar cell. The silicon solar cell absorbs all low energy light and together, both layers use more of the energy in the solar spectrum for energy generation. So far, the transfer of energy is the main bottleneck in this process. In this thesis we first describe a way to use quantum dots as a layer that facilitates the energy transfer in between the Singlet Fission layer and silicon. Then, we describe a new optical method to detect the transfer of energy. We also manufacture a real-world Singlet Fission-Silicon solar cell and use the special behavior of the Singlet Fission process under a magnetic field to detect the energy transfer, and show that the change in the crystal structure in the Singlet Fission material is responsible for the transfer of energy. With these new techniques and insights, we hope that real life Singlet Fission-silicon solar cells have become closer to realization.