Dear Shuen,

Since the interaction with lattice will be temperature dependent, it is quite understandable that the positions, splitting and the life times of various energy levels of an activator can be temperature dependent. It is quite common to find that at lower temperatures the host lattice offers conditions conducive for luminescence while at high temperatures, the non-radiative processes become dominant. This has been termed as thermal quenching. For many applications it assumes prime importance. It determines the operating temperature of the device based on the luminescent material. In some cases (e.g. Y2O3:Eu) increase in luminescence efficiency at high temperatures has been observed. This occurs due to the thermal quenching of the processes, which compete with the desired emission.

For more information please read following very important book

Luminescent Materials - Prof. Dr. G. Blasse, Prof. Dr. B. C. Grabmaier (1994)

Are you measuring in molecular or solid state materials?

The photoluminescence yield (Y) depends on the radiative (kR) and nonradiative rates (kNR)

(Y) = kR/(kR+KNR)

In a simple molecular system, temperature largely effects the Boltzmann distribution of population of states in the ground and excited states, and so the internal conversion rates. Intersystem crossing to for example triplet states can also be thermally activated and therefore temperature dependent. These are both manifest as a change in the radiative lifetime of the system, as they largely influence the non radiative processes.

I am not sure what you mean by quenching.

In liquids or gases, quenching can occur by additional mechanisms or molecular collisions - which are temperature dependent.

In solids, excitons can be more mobile in a solid at elevated temperatures, and can be subject to higher quenching probability doe to defect or surface states.

Dear Wei Shuen,

Your question sounds easy but is hard to answer. There is, as you certainly knows, a large amount of available experimental data about the strong temperature dependence of (solid state) luminescence, nevertheless its mechanism is still not well understood.

The temperature quenching is a major limitation in the achievement of intense room-temperature luminescence. This decrease can be attributed to many factors involving matters like a reduced pumping efficiency, the number of available excitable optically active sites or an increase of nonradioactive deexcitation processes.

The following reference might be of interest to you:

https://www.researchgate.net/profile/Pieter_Dorenbos/publication/27342419_Thermal_Qenching_of_Eu2_5d-4f_Luminescence_in_Inorganic_Compounds/links/02e7e519fda9c2a8b1000000/Thermal-Qenching-of-Eu2-5d-4f-Luminescence-in-Inorganic-Compounds.pdf

This study uses and discuss a rule for series of alkaline earth compounds based on the so-called quenching temperature T0.5, i.e. the temperature at which the emission intensity has dropped to 50% of the low temperature value.

A modelling attempt of the thermal quenching mechanism in quartz is described in the following paper:

https://pdfs.semanticscholar.org/a48f/6eb36aa85f17935f1fc28bc6240e778b4178.pdf

A very interesting paper, from the famous lab of prof. dr. G. Blasse and his successor prof. dr. Meijerink, discussing thermal quenching models might be of interest to you:

https://dspace.library.uu.nl/bitstream/handle/1874/272480/nn303217q.pdf?sequence=2

This link corresponds to:

Zhao, Y., Riemersma, C., Pietra, F., Koole, R., de Mello Donegá, C., & Meijerink, A. (2012). High-temperature luminescence quenching of colloidal quantum dots. ACS nano, 6(10), 9058-9067.

Hope this info is of any help to you.

From my perspective, I think quenching rate may be evaluated from the decrease rate of luminescence versus time at a certain temperature. You can define your own rule for luminescence quenching rate, not limited to the literature review.

Or you can define the quenching rate as a function of temperature, say: 1 nW/℃.

Just my suggestion~