Magnetic field effect of the singlet fission reaction in tetracene-based diodes

We investigate the magnetophotocurrent (MPC) response in tetracene-based diodes and attribute the initially decreasing and then increasing MPC responses to the feature of the singlet fission (SF) reaction (a magnetic field sensitive process) as modulated by the applied magnetic field in the tetracene active layer. The SF reaction is further characterized by the magnetophotoluminescence (MPL) measurement of the tetracene film, in which the variation of MPL is correlated with the change of MPC response in the device. However, the SF reaction of the singlet excitons in the tetracene would compete with the separation of the opposite charge carriers at the donor/acceptor interfaces by depositing the fullerene (C-60) on the tetracene active layer to yield a planar heterojunction. Our results indicate that the charge separation is more effective than the SF reaction. The dissociation and the charge reaction processes of the charge transfer complexes at donor/acceptor interfaces dominate the photocurrent as well as MPC response in tetracene/C-60-based diodes.