Solution-processable triplet exciton harvesting blue and orange emitters for a high-efficiency, color-stable, simple-structured white fluorescent organic light-emitting diode

Abstract

The utilization of triplet excitons is of considerable attention for high-efficiency fluorescent organic light-emitting diodes (OLEDs). Here, two solution-processable triplet exciton harvesting emitters (CPhCN and CBzTPA) are reported. They are designed and synthesized by connecting a highly soluble tercarbazole moiety to a donor-acceptor fragment of 4-(triphenylen-2-yl)benzonitrile for CPhCN and 4-(benzo[c][1,2,5]thiadiazol-4-yl)-N,N-diphenylaniline for CBzTPA. The photophysical studies and theoretical calculations prove that CPhCN is a triplet-triplet annihilation (TTA)-based sky blue emitter and CBzTPA is a hybridized local and charge-transfer (HLCT)-based orange emitter with decent solid-state photoluminescence quantum yields. Due to their commendable hole mobility, high solubility, and thermal stability, these compounds are effectively utilized as non-doped emitters in solution-processed blue and orange OLEDs, achieving satisfactory device performances. Notably, white light-emitting OLED utilized a compatible blend film of CPhCN and CBzTPA (99.24: 0.76) as a single emissive layer successfully produces white light emission with the CIE coordinates of (0.315, 0.372) and exceptional color stability across various applied voltages, and achieves outstanding electroluminescent performance with a maximum external quantum efficiency (EQEmax) of 9.43%. This work offers valuable guidance for the development of a high-efficiency, color-stable solution-processed white fluorescent OLED.