Abstract
Energy transfer and singlet (re)generation from triplets are studied via time-resolved electroluminescence (EL) measurements for a near-infrared-emitting, porphyrin hexamer-based host-guest organic light-emitting diode (OLED), with the porphyrin as the guest and PIDT-2TPD as the host, via time-resolved EL measurements. Energy transfer mechanisms from the host to the guest molecules are observed in the studied system in the evolution of the EL emission spectra over and following 1 microsecond driving voltage pulses. Residual EL from the guest molecule with no driving voltage over long timescales (order of several microseconds) is also observed, thereby providing clear evidence of singlet (re)generation over characteristic times similar to triplet lifetimes, consistently with triplet-triplet annihilation (TTA) and/or reverse inter-system crossing (rISC) taking place. This had never been reported before for PIDT-2TPD.