Thermally activated delayed fluorescence (TADF) has attracted much attention for realization of highly-efficient and low-cost organic light emitting diodes (OLEDs). OLEDs based on 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN), which is one of highly-efficient TADF emitters, have been demonstrated to exhibit external quantum efficiency more than 19%. To study the decay rates from excited states of 4CzIPN, the temperature dependence of photoluminescence quantum efficiency (PLQE) has been measured in the weak photoexcitation limit in 4CzIPN-doped 1,3-bis(9-carbazolyl)benzene thin films. Characteristic features of the temperature dependence of PLQE in the weak photoexcitation limit are found, and examined by using rate equations of singlet and triplet densities.
2016 by The Imaging Society of Japan