Organic multi exciton generation augmented silicon (OMEGA): Elucidating hybrid inorganic-organic energy transfer

Current silicon photovoltaics are approaching the single-junction efficiency limit, which is largely imposed by the inevitable thermalization losses caused as above-gap photocarriers relax to the band-edge prior to extraction. These losses could be mitigated if the excess energy of a photon could instead be used to produce an additional excitation, and organic molecular singlet fission has been touted as a highly efficient method of multi-exciton generation towards this goal. Harvesting the nascent triplets in a silicon cell via transfer across an appropriately designed interface could then lead to improved photocurrent. An alternative approach is to radiatively couple a chromophore to silicon via quantum cutting, wherein the absorption of a high-energy photon leads to emission of two down-converted photons closer to the silicon band gap. Here, I will discuss our efforts to design augmented silicon devices via singlet fission, with an emphasis on the effect of the interface between the organic chromophore and silicon. Through magnetic field-dependent photocurrent and photoluminescence measurements, we identify systems which allow for triplet energy transfer into silicon solar cells. We further identify the band alignment requirements necessary to enable triplet energy transfer and how this progresses towards commericalising singlet fission solar cells.