Dear Joan

You raise a great question about the phosphorescent or gerenal OLED degradation issues. Generally speaking when operating temperature is increased, the luminance or brightness of an OLED is decreased. There are some patents you should be able to find it. This type of work is regularly done in industry and hardly in academic community. Hope it helps.

Xuhua

Dear Xuhua Wang,

many thanks! I understand that the luminance would decrease with temperature over time due to an acceleration of anydegradation mechanisms. But, intrinsically and omitting degradation, what should be the behavior?

Anyway, I'll take a look on the patents, indeed. Thanks a lot!

Joan

Increased temperature will cause increased molecular vibrations. So vibrational relaxations would de-excite the excited triplet states very fast through non radiative processes.

Thanks! That is what I would expect yes, but I'd like to see also some data on actual devices...

Thanks!

I investigated the effect of the temperature on the wavelength of the radiated photons from the LEDs, however the metallic LEDS.I found there will be a red shift with increases temperature. Please follow the link: https://www.researchgate.net/post/How_are_the_wavelength_of_LEDs_dependent_on_temperature

I would expect a similar behavior of the organic materials as the temperature stretches the bond between the spices of the organic molecules.

Best wishes

Thank you Prof. Zekry for your reply. I had also noticed a shift in the spectra, however, in my case it was a small blue shift as temperature increases . I also measured decrease luminance as T increases, as indicated by the previous answers. Regarding the blue shift, I think it is expected in organic semiconductors, though I haven't investigated further.

best,

Joan