Singlet Fission for Photovoltaics with 130 % Injection Efficiency

Abstract

Abstract A novel pentacene dimer ( P2 ) and a structurally analogous monomer ( P1 ) were synthesized for use in n‐type dye‐sensitized solar cells. In P2 , the triplet excited states formed by the rapid, spin‐allowed process singlet fission were expected to enable carrier multiplication in comparison to the slow, spin‐forbidden intersystem crossing seen in P1 . A meta ‐positioning of the two pentacenes and the carboxylate anchor were chosen in P2 to balance the intramolecular dynamics of singlet fission and electron injection. Electron injection from energetically low‐lying triplet excited states of pentacene units necessitated the intrinsic and extrinsic lowering of the Fermi level of the semiconductor. Indium‐zinc oxide in the presence of Li + was found to be the optimum choice for the photoelectrodes. Efficient electron injection from the triplet excited states of P1 and P2 was found, with a carrier multiplication of nearly 130 %.