Controlling reabsorption effect of bi-color CdSe quantum dots-based white light-emitting diodes

Cyuan Bin Siao, Shu Ru Chung, Kuan Wen Wang

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

1 Scopus citations


The colloidal semiconductor quantum dots (QDs) have the potentials to be used in white light-emitting diode (WLED) as a down-converting component to replace incandescent lamps, because the traditional WLED composed of Y3Al5O12:Ce3+ (YAG:Ce) phosphor lack of red color emissions and shows low color quality. Among various QDs, CdSe has been extensively studied because it possesses attractive characteristics such as high quantum yields (QYs), narrow emission spectral bandwidth, as well as size-tunable optical characteristics. However, in order to enhance the color rendering index (CRI) of WLED, blending materials with different emission wavelengths has been used frequently. Unfortunately, these procedures are complex and time-consuming, and the emission energy of smaller QDs can be reabsorbed by larger QDs, resulting in decreasing the excitation intensity in yellowish-green region. Therefore, in this study, in order to decrease the reabsorption effect and to simplify the procedures, we have demonstrated a facile thermal pyrolyzed route to prepare bicolor CdSe QDs with dual-wavelengths. The emission wavelengths, particle sizes, and QYs of QDs can be tuned from 537/595 to 537/602 nm, 2.59/3.92 to 2.59/4.01 nm, and 27 to 40 %, for GR1 to 3 samples, respectively when the amount of Se precursor is decreased from 1.5 to 0.75 mmol. Meanwhile, the area ratio of green to red (Ag/Ar) in fluorescence spectra is gradually increased, due to the increase in growth rate, and decrease in nuclei formation in red emission. The GR1, GR2, and GR3 QDs are then encapsulated by convert types to form the LED, in which the QDs are deposited on the blue-emitting InGaN LED chip (λem = 450 nm). After encapsulation, the devices properties of Commission International d'Eclairage (CIE) chromaticity and Ag/Ar area ratio are (0.40, 0.24), 0.28/1, (0.40, 0.31), 0.52/1, and (0.40, 0.38), 1.02/1, respectively for GR1, GR2, and GR3. The results show that the green emission intensity are strongly reabsorbed by red emission, as the Ag/Ar area ratios are gradually increased and the CIEs are dramatically shift to white light region, suggesting that the Se amount not only can tune the red emission intensity but also can decrease the reabsorption effect. Based on the above results, the GR3 is suitable to be applied for WLED against the reabsorption effect. Besides, when the GR3 is blended with UV resin of 30 wt. % to prepare the WLED, the CIE located at (0.35, 0.34) is applied as backlight source, providing 126 % color gamut in sRGB standard. As a result, by simply adjusting the concentration of Se precursor, QDs with dual-wavelengths can be prepared and the reabsorption effect can be avoided to show promising lighting properties for the application in WLED.

Original languageEnglish
Title of host publicationLow-Dimensional Materials and Devices 2017
EditorsA. Alec Talin, Albert V. Davydov, M. Saif Islam, Nobuhiko P. Kobayashi
ISBN (Electronic)9781510611559
StatePublished - 2017
EventLow-Dimensional Materials and Devices 2017 - San Diego, United States
Duration: 9 Aug 201710 Aug 2017

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceLow-Dimensional Materials and Devices 2017
Country/TerritoryUnited States
CitySan Diego


  • CdSe
  • Dual-wavelengths
  • Quantum dots
  • Reabsorption effect
  • White light-emitting diode


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