Low-temperature annealing to enhance efficiency in organic small-molecule solution-processable OLEDs

Single-layer solution-processable organic light-emitting diodes (OLEDs) based on a green emissive molecule of 4,7-bis(9,9-bis(6-9H-carbazol-9-yl)hexyl)-9H-fluoren-2-yl)benzo[c][1,2,5] thiadiazole (TCBzC) are fabricated. The luminous efficiency reaches 6.9 cd A−1 after annealing at low temperature of 40 °C, which is double that of the un-annealing device, and this performance is among the highest efficiency of single-layer solution-processable OLEDs reported so far. This enhancement may be due to rearrangement of the peripheral alkyl-linked carbazole units in TCBzC after annealing, which helps the hole and electron transport to be more balanced