  Singlet fission in tetracene generates two triplet excitons per absorbed
photon. If these triplet excitons can be effectively transferred into silicon
(Si) then additional photocurrent can be generated from photons above the
bandgap of Si. This could alleviate the thermalization loss and increase the
efficiency of conventional Si solar cells. Here we show that a change in the
polymorphism of tetracene deposited on Si due to air exposure, facilitates
triplet transfer from tetracene into Si. Magnetic field-dependent photocurrent
measurements confirm that triplet excitons contribute to the photocurrent. The
decay of tetracene delayed photoluminescence was used to determine a triplet
transfer time of 215 ns and a maximum yield of triplet transfer into Si of ~50
%. Our study suggests that control over the morphology of tetracene during
deposition will be of great importance to boost the triplet transfer yield
further.
