Hybrid pentacene/a-silicon solar cells utilizing multiple carrier generation via singlet exciton fission

Silicon dominates the solar cell market because of its abundance, mature production processes, and high efficiencies, with the best solar cells approaching the Shockley-Queisser limit. Multiple exciton photogeneration provides a route to solar cells that surpass the Shockley-Queisser limit, and we report the use of pentacene, for which photogenerated singlet excitons rapidly convert into two lower-energy spin-triplet excitons. We report solar cells that couple amorphous silicon to pentacene. We show that a thin layer of nanocrystals between silicon and pentacene allows simultaneously harnessing low-energy photons absorbed in silicon and high-energy photons absorbed in pentacene, generating two excitons via singlet fission. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4757612]