I don't know what the mechanism is, but this [1] article describes the spectrum depending on both temperature and current [1] https://www.researchgate.net/publ

I don't know what the mechanism is, but this [1] article describes the spectrum depending on both temperature and current [1] https://www.researchgate.net/publication/250139383_Dependence_of_Emission_Spectra_of_LEDs_upon_Junction_Temperature_and_Driving_Current https://www.researchgate.net/publication/250139383_Dependenc...