The lighting market has been dominated by light emitting diodes (LEDs), which not only need Ga for wafer production, but also consume abundant non-sustainable rare-earth elements such as Y, Ce and Eu. Hybrid-LED technology using organic downconversion materials (ODMs) is a promising candidate technology to save the rare-earth elemental resources. However, it is still a challenge to fabricate hybrid-LED devices with a high color rendering index (CRI), lumen efficiency and long lifetime at the same time. Herein, highly dispersible perylene diimides are synthesized in short routes and dispersed into a polymer matrix at high temperature to produce low cost light ODMs. Cold to warm white LED lamps with a CRI up to 92 can be fabricated with the ODMs. In particular, a warm white lamp with the same high CRI and efficiency up to 82 lm W−1 is obtained. It is comparable to all inorganic warm white LEDs with such a high CRI. By applying our OMDs, an approach for highly efficient yellow LED lamps, which can improve efficiency by 66% to 153 lm W−1 compared with the present method, is illustrated. More importantly, incorporating a remote phosphor configuration (RPC) effectively improves the lifetime of ODMs superior to 2870 h, extrapolated to 6000 h maintaining 70% of the original fluorescence efficiency after continuous operation in an ambient environment. This approach could be a quite simple protocol paving the way for the practical application of hybrid-LED lamps.
Solid-phase color converter-based quantum dots (QDs) white light-emitting diodes (WLEDs) have become promising next-generation solid-state light sources. However, the development of these WLEDs’ production still suffers from constraints involving insufficient color-rendering index (CRI), low color stability, and short operation lifetimes. Here, thick-shell Cd 0.05 Zn 0.95 S/CdSe/Cd x Zn 1– x S spherical quantum wells are developed with good color tunability from green to red regions and high photoluminescence quantum yield (up to 88% for green wavelengths). QDs with five emission colors are used to fabricate a series of WLEDs, which possess a good correlated color temperature tunability from warm (3210 K) to cool (22 000K) white light, and a high CRI Ra (>90). Specifically, the neutral white light device with Commission Internationale de l´Eclairage (CIE, International Commission on illumination) of (0.36, 0.36) and the standard white light device with CIE of (0.33, 0.33) achieve a CRI Ra up to 95.8 and 95.11, respectively, they also exhibit long operating life and great color stability. These results indicate that the improvement of the performance and stability of the WLED based on thick-shell spherical quantum wells is remarkable progress in the commercialization of QD-based solid-state lighting.
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