Luminance enhancement of color stabilized organic light-emitting devices with an active layer containing CdSe/CdS/ZnS...

Organic light-emitting devices (OLEDs) with a 1,3-bis(9-carbazolyl)benzene (mCP) or a (9-(3-(9 H-carbazol-9-yl)phenyl)-9 H-carbazol-3-yl)-diphenylphosphine oxide (mCPPO1) layer containing CdSe/CdS/ZnS quantum dots (QDs) were fabricated. The average diameter of core/shell/shell QDs, as determined from transmission electron microscopy measurements, was approximately 7 nm. The photoluminescence spectrum for the CdSe/CdS/ZnS QDs showed a dominant exciton peak. Current densities as functions of the voltage showed that the turn-on voltage of the OLED with an mCP layer containing QDs was as small as 5 V, and the luminances as functions of the voltage showed that the luminance of the OLED with an mCP layer containing QDs was much larger than that of the OLED with an mCPPO1 layer containing QDs. Electroluminescence spectra for OLEDs with an mCP layer containing QDs showed that the dominant exciton peaks corresponding to the QDs were located at almost the same positions, regardless of the applied voltage. These results help to understand the electrical and optical properties of OLEDs with an mCP or an mCPPO1 layer containing CdSe/CdS/ZnS core/shell/shell QDs.