Spin-triplet exciton impact on electrical devices

The magnet-field modulated response of electronic devices gives us insight into the spin dynamics in materials. In organic semiconductors, the dynamics of spontaneous singlet fission/triplet fusion can be observed using the magnetic field modulated electro-luminescence (MEL) or photocurrent (MPC). In this talk, we present results which show singlet fission and triplet fusion processes though the observation of MEL and MPC signals from organic light emitting diodes and organic transistors. For the semiconductor diF-TES-ADT (2,8-Difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene) we observe that a polycrystalline film in an OLED produces an MEL signal which is similar to the angle-averaged MPC of a single crystal transistor. We use a simple model to calculate response and find that signal from both devices is directly related to the overlap in spin character of the triplet and singlet states that drives both the singlet fission in the MPC response and triplet fusion in the MEL response. The MEL/MPC response between 0 mT and 200 mT is primarily dependent on the zero-field splitting (magnetic dipole) of the triplet excitons.