I would like to get the physical meaning of exciton quenching in solar cells.
Dear Shamjid Palappra, let me encourage you to take a good book on solid state / semiconductor physics and to study that until you have really understoof what an exciton actually is (unless you are confident that this is already the case).
You will then understand that an exciton is (in principle) an excited stationary state. If in reality it were truly stationary, it would live forever, which it doesn't. Nevertheless, if it is long lived, then its energy is pretty well defined (in some analogy to e.g. atomic excited states). As a consequence the optical absorption to the excitonic state will be characterized by a narrow peak. Any process reducing the lifetime of the exciton (see Behnam's post) will broaden that peak (and accordingly reduce its hight). You may consider the exciton as quenched, when the lifetime is si short that you can't identify its absorption peak any more.
To build some further bridge to what Behnam wrote: in the situation I described as "quenched", consider thet the exciton state is "reached" in some other manner (e.g. energetic electronic collisions or relaxation after a higher energy optical excitation). If it's lifetime is so short, it will quickly cease to exist and shall not give rise to fluorescence at a well defined energy.
Here is the answer:
http://en.wikipedia.org/wiki/Quenching_%28fluorescence%29
In essence, in particular as regards excitons, "quenching" refers to any process of non-radiative energy transfer.
The details in this text
http://dissertations.ub.rug.nl/FILES/faculties/science/2006/d.e.markov/06_c6.pdf
which has been officially published here
http://scitation.aip.org/content/aip/journal/apl/87/23/10.1063/1.2139622
may prove instructive. Similarly as regards this news item:
http://phys.org/news194506432.html
Dear Shamjid Palappra, let me encourage you to take a good book on solid state / semiconductor physics and to study that until you have really understoof what an exciton actually is (unless you are confident that this is already the case).
You will then understand that an exciton is (in principle) an excited stationary state. If in reality it were truly stationary, it would live forever, which it doesn't. Nevertheless, if it is long lived, then its energy is pretty well defined (in some analogy to e.g. atomic excited states). As a consequence the optical absorption to the excitonic state will be characterized by a narrow peak. Any process reducing the lifetime of the exciton (see Behnam's post) will broaden that peak (and accordingly reduce its hight). You may consider the exciton as quenched, when the lifetime is si short that you can't identify its absorption peak any more.
To build some further bridge to what Behnam wrote: in the situation I described as "quenched", consider thet the exciton state is "reached" in some other manner (e.g. energetic electronic collisions or relaxation after a higher energy optical excitation). If it's lifetime is so short, it will quickly cease to exist and shall not give rise to fluorescence at a well defined energy.
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