Prospects and challenges for nanocrystal lumophores that emit light with quantum yield approaching the thermodynamic limit

Lumophores that logarithmically approach unity quantum yield are important components for future energy conversion devices such as luminescent concentrators, optical refrigerators, and down converting solar greenhouses. This talk will review the potential for colloidal nanocrystal quantum dots to meet the requirements as lumophores for such demanding applications. The case of CdSe@CdS quantum dots will be contrasted with cesium lead halide perovskite nanocrystals. The new photothermal threshold quantum yield measurement technique will be introduced as well. This method can presently distinguish a part in 1000 deviation below unity quantum yield, and may soon be able to see parts in 10000. With these techniques, the influence of even one individual surface defect can be seen, and can provide a stringent test for the limits of nanocrystal lumophores.