Ocean’s Blue LEDs
Figure 1. Electroluminescence spectrum of the QD-LED measured at the bias of 5.5 V. Insets: photomicrographs of the LED surface recorded at the brightnesses of 100 and 1600 cd/m2.
Ocean NanoTech and collaborators developed a multilayer solution-processed blue light-emitting diode based on colloidal core/shell CdS/ZnS nanocrystal quantum dots (QDs). At a low-operating voltage of 5.5 V, the device emits spectrally pure blue radiation at 460 nm with a narrow full-width-at-half-maximum bandwidth of 20 nm and high brightness up to 1600 cd/m2. Broad-band, long-wavelength emission from the polymer components and deep traps in the QDs are minimized to less than 5% of the total emission.
The QD-LED in this experiment was configured with a multiple layer structure employing structurally engineered Ocean NanoTech core/shell CdS/ZnS QDs in the emissive region. At a low operation voltage of 5.5V, the device emitted pure blue light with a strikingly narrow fwhm bandwidth of 20 nm and a high brightness up to 1600 cd/m2. The long wavelength tail of the LED output was minimized to less than 5% of the total emission, leading to the highly saturated blue emission from QD-LEDs. The result of our blue-LED study represents a significant improvement over the performance of existing blue QD-LEDs and marks a further step toward the practical application of QD-LED technology in full-color display and solid-state lighting.
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*Zhanao Tan, Fan Zhang, Ting Zhu, Jian Xu, Andrew Y. Wang, John D. Dixon, Linsong Li, Qi Zhang, Suzanne E. Mohney, Jerzy Ruzyllo, “Bright and Color-Saturated Emission from Blue Light-Emitting Diodes Based on Solution-Processed Colloidal Nanocrystal Quantum Dots,” Nano Letters, 7(12), 3803-3807, 2007.