Colloidal Nanocrystals with Excellent Thermal and High-Flux Stability

Solid-state lighting (SSL) has the potential to revolutionize the lighting industry. Light-emitting diodes (LEDs)--traditionally used in signs, signals and displays--are rapidly evolving to provide light sources for general illumination. This technology holds promise for lower energy consumption and reduced maintenance.  However the solid state Lighting industry employs rare-earth containing inorganic compounds as the phosphor down converters.　 Due to the short supply of rare-earths, these converters are becoming expensive.　 These conventional phosphors are also difficult to tune, scatter light excessively, have broad spectral widths, and for some products, can suffer both from thermal and high flux quenching.  UB researchers have resolved this problem by formulating a novel semiconductor nanocrystals to replace the phosphor. The novel semiconductor solved two fundamental problems 1) The loss of quantum efficiency (QE) at elevated temperatures and 2) The loss of QE at high excitation optical power densities. Typically, nanocrystals are well-known to suffer from high-optical flux saturation as a result of Auger recombination (Y. Park et al., Phys. Rev. Lett. 106, 187401 (2011)) and blinking phenomena (I Chung at al., Phys. Rev. B70, 165304 (2004)) which impact on the fluorescence efficiency of nanocrystals. The invented novel nanocrystals demonstrate both temperature (at least up to 150 °C) and high-flux (at least up to 20 kW/cm2 of cw-excitation) stable quantum efficiencies. In addition, pulsed excitation measurements indicate that they enable a shutdown of Auger recombination at least up to an average excitation level of 3 e-h pairs. The total SSL market is expected to reach $56.79 billion by 2018, at a Current Annual Growth Rate of 18.7% from 2013 to 2018. Patent Link: US9153731