PROCEEDINGS ARTICLE | February 6, 2012
Proc. SPIE. 8278, Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XVI
KEYWORDS: Light sources, Light emitting diodes, Photons, Quantum efficiency, Quantum dots, General lighting, Line edge roughness, Luminous efficiency, Systems modeling, Blue light emitting diodes
For high-quality general lighting, a white light source is required to exhibit good photometric and colorimetric
performance along with a high level of electrical efficiency. For example, a warm white shade is desirable for indoors,
corresponding to correlated color temperatures ≥4000 K, together with color rendering indices ≥90. Additionally, the
luminous efficacy of optical radiation (LER) should be high, preferably ≥380 lm/Wopt. Conventional white LEDs cannot
currently satisfy these requirements simultaneously. On the other hand, color-conversion white LEDs (WLEDs)
integrated with quantum dots (QDs) can simultaneously reach such high levels of photometric and colorimetric
performance. However, their electrical efficiency performance and limits have been unknown. To understand their
potential of luminous efficiency (lm/Welect), we modeled and studied different QD-WLED architectures based on layered
QD films and QD blends, all integrated on blue LED chips. The architecture of red, yellow and green emitting QD films
(in this order from the chip outwards) is demonstrated to outperform the rest. In this case, for photometrically efficient
spectra, the maximum achievable LE is predicted to be 327 lm/Welect. Using a state-of-the-art blue LED reported with a
power conversion efficiency (PCE) of 81.3%, the overall WLED PCE is shown to be 69%. To achieve LEs of 100, 150
and 200 lm/Welect, the required minimum quantum efficiencies of the color-converting QDs are found to be 39, 58 and
79%, respectively.
