Singlet Exciton Fission Sensitization of Silicon Photovoltaics

The efficiencies of crystalline silicon solar cells, the current industry standard for photovoltaics, are approaching the Shockley-Queisser limit. One method of going beyond this limit is to sensitize the silicon (Si) by using organic molecules that can perform singlet exciton fission (SF), a carrier multiplication process that can create two triplet excitons (electron-hole pairs) from a single photon. Successful transfer of these two triplet excitons to silicon can result in increased photocurrent and improved efficiencies.<br/> <br/>Previous work has shown coupling between Si and the archetype singlet exciton fission material tetracene in the presence of passivating interfacial layers of hafnium oxynitride through magnetic-field dependent photocurrent [1]. However, the electrical device performance did not show an enhancement from tetracene due to insufficient passivation and poor carrier extraction from the surface [1]. We have developed a new interfacial heterostructure that both provides surface passivation of defects and facilitates intermediate charge transfer states for triplet exciton transfer from tetracene to silicon. Additionally, using silicon photovoltaic device architectures with shallow junctions and high carrier extraction efficiency at the surface, we demonstrate enhancements in short circuit current from singlet exciton fission in tetracene for the first time.<br/> <br/>[1] Einzinger, M., Wu, T., Kompalla, J.F. <i>et al.</i> Sensitization of silicon by singlet exciton fission in tetracene. <i>Nature</i> <b>571,</b> 90–94 (2019).