Solution-processed white organic light-emitting diodes with blue fluorescent and orange-red thermally activated delayed fluorescent dendritic luminogens

In this work, dendritic luminogens, namely, 3ICz-Tr as a blue emitter and Tri-tNID as an orange-red emitter, were synthesized and used for the application of white organic light-emitting diodes (WOLEDs). These molecules have appropriately high molecular weights, which are favorable for the fabrication of thin films with fine surface morphologies. Interestingly, the blue emitting 3ICz-Tr displays fluorescent character and the orange-red emitting Tri-tNID exhibited thermally activated delayed fluorescence, which was confirmed by steady state and transient photoluminescence (TRPL) spectroscopy. Eventually, WOLED devices could be realized by mixing the two molecules and optimizing their mixture composition. Among the devices we fabricated, the device with Tri-tNID and 3ICz-Tr (0.5:99.5 wt ratio) without additional host material demonstrated nearly pure white emission, with the maximum EQE of 8.32% and CIE coordinate of (0.32, 0.30). Furthermore, by changing the composition of the two dendritic molecules, the emission color can be adjusted from a warm white to a cool white in the corresponding WOLED.