Scientists demonstrate new, improved way to make infrared light, with quantum dots

 https://phys.org/news/2023-09-scientists-infrared-quantum-dots.html

"very efficient and easy to make... cascade technique... created black ink of trillions nanocrystals, spread it onto surface and sent electricity through, electrons travel through series of distinct energy levels, like falling down series of waterfalls. Each time electron falls down an energy level, it has chance to emit some energy as light... works because of quantum mechanics... infrared lasers and cost-effective sensors, especially exhaust emissions tests, and breathalyzers"