Highly-efficient LEDs by Combining Traditional Phosphors with InP/ZnSe Red Quantum Dots: Impact of Quantum Efficiency
We report efficient, high-CRI white LEDs with an on-chip color convertor coating based on red InP/ZnSe QDs and traditional green/yellow powder phosphors. Using InP/ZnSe QDs with a quantum yield of nearly 80% and a full width at half maximum of 45 nm, we demonstrate high spectral efficiency for white LEDs with very high CRI values. The white LED that we made has an efficacy of 132 lm/W, and color rendering indices of Ra ~ 90, R9 ~ 50 for CCT ~ 4000 K. Further, we show that this result would be significantly higher with a ‘state-of-the-art’ LED package, as the main losses are due to the non-optimal wall-plug efficiency of the blue LED chip and non-optimal recycling properties of the package used in this study. To make efficient LEDs, it is also important to carefully choose a green powder phosphor that does not emit significantly in the red region, and that quantum dots are of high efficiency