Polymer and small molecule mixture for organic hole transport layers in quantum dot light-emitting diodes

The performance of quantum dot light-emitting diodes (QD-LEDs) was investigated for different hole transport layers with small molecules and polymers: poly(4-butyl-phenyl-diphenyl-amine), poly-N-vinylcarbazole (PVK), N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-diphenyl-4, 4′-diamine, 4,4′,4″-tris(N-carbazolyl)-triphenyl-amine (TCTA), and 4,4′-bis(carbazole-9-yl)biphenyl (CBP). The electroluminescence performance of QD-LEDs was considerably improved by adding small molecules (TCTA or CBP) having high hole mobilily to the polymer hole transport material (PVK). The maximal current efficiency of QD-LED-based PVK was improved by 27% upon addition of 20 wt % TCTA due to the hole injection improvement. The lower turn-on voltage, the higher current density, and the higher luminance were achieved by addition of TCTA. The maximal luminance of 40900 cd/m² and the highest current efficiency of 14.0 cd/A with the narrow full width at half-maximum (<35 nm) were achieved by the best hole transport layer.