Hi,
In order to enhance the luminescence efficiency of a phosphor it seems that the activator concentration in the host should be as high as possible. However, it is found that the luminescence efficiency decreases if the activator concentration exceeds the specific value known as critical concentration. This effect is called as concentration quenching. When the concentration of dopant is low enough then it can be consider as an isolated centre in the host system. However, with the increase of dopant or co-dopant concentrations, the ion centers are sufficiently close together to interact and the strong interaction between two active ions are able to transfer the excitation energy from one to another. Therefore the the probability of energy transfer exceeds that for emission then the excitation energy repeatedly goes from the one activator to the other and eventually lost at the surface, dislocations or impurities. Thus, it makes no contribution to the luminescence. The efficiency then decreases in spite of the increase of the activator concentration.
Hope this clears your doubt regarding concentration quenching.
Hi,
In order to enhance the luminescence efficiency of a phosphor it seems that the activator concentration in the host should be as high as possible. However, it is found that the luminescence efficiency decreases if the activator concentration exceeds the specific value known as critical concentration. This effect is called as concentration quenching. When the concentration of dopant is low enough then it can be consider as an isolated centre in the host system. However, with the increase of dopant or co-dopant concentrations, the ion centers are sufficiently close together to interact and the strong interaction between two active ions are able to transfer the excitation energy from one to another. Therefore the the probability of energy transfer exceeds that for emission then the excitation energy repeatedly goes from the one activator to the other and eventually lost at the surface, dislocations or impurities. Thus, it makes no contribution to the luminescence. The efficiency then decreases in spite of the increase of the activator concentration.
Hope this clears your doubt regarding concentration quenching.
https://www.youtube.com/watch?v=snBLWT0U_8Y&list=PLQLtIQhMOBQ7QVRZKtbZfw5KqNSqg6FTG&index=21
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