Daryl Hawkes1 MingLee Tang1

1, University of California, Riverside, Riverside, California, United States

Third-generation photovoltaics seek to improve solar technology, potentially beyond the Shockley-Queisser limit. One proposed method to achieve this goal, is to generate multiple excitons per absorbed photon. Multiple exciton generation in quantum dot photovoltaics, and singlet fission in organic photovoltaics have been able to produce photovoltaic external quantum efficiencies above one hundred percent. In addition, these processes have the potential to improve solar cell efficiency by generating additional photocurrent from these multi-exciton processes. This work seeks to create a hybrid nanoparticle-ligand system as the active absorbing layer in a p-n heterojunction solar cell. This active layer will utilize strongly absorbing PbS nanocrystals, with bidentate derivatives of diphenylhexatriene (DPH) functionalized with carboxylic acid linkers as ligands capable of replacing the native ligands on the nanocrystal. DPH in the solid state has shown singlet fission quantum yields of 90% and triplet lifetimes greater than 50 microseconds. By designing PbS nanocrystals with conduction bands below the triplet energy of the DPH analogs, triplet excitons generated in the DPH ligands can transport into the PbS nanocrystals and then undergo charge separation and transport to their respective electrodes. The purpose of this work is to observe singlet fission at the nanocrystal-ligand interface and use the triplets generated to produce additional photocurrent in a photovoltaic device.