I have not seen any reports based on shelling of semiconductor nanocrystals with metal. In your opinion, do you think shelling a semiconductor nanocrystal(CdSe, CdS, CZTS) with metal(say Au or Ag) can improve a thin film solar cell?
Depending on the two compounds selection, a numerous chemical and physical properties can be realized in these systems. Metal-semiconductor core-shell nanoparticles in particular are the focus of intensive research due to their enhanced optical properties. For example, it is believed that matching the surface plasmon resonance excitation energy of the metal nanoparticle core to the band gap energy of the semiconductor shell leads to more efficient energy transfer between the semiconductor coating and the metal cores.
These advantage is not limited to metal-semiconductor core-shell nanoparticles. For instance, a narrow band gap semiconductor nanoparticle can be surrounded with a wide gap material to prevent the formation of surface traps, leading to enhanced band edge luminescence in the core-shell system. Alternatively, the shell material can be chosen to improve the chemical stability of the core, which is important for medical imaging applications.
Thanks for the response. But, what about vice-versa? Do you think the surface defects can be controlled by coating a semiconductor nanocrystal with metal? There has been extensive research on metal core with semiconductor around it as a shell. But what about the other way round? It changes the properties.
If you put a metal around a semiconducting particle the metal will absorb all the light - and rapidly convert the energy to heat. You won't get any generation of electron hole pairs in the semiconductor, so I think it's a pretty useless approach for solar cells.
But what about if you have a thin caged network around the semiconductor? Say, a nanocage with no direct contact with the semiconductor, do you think it can serve as an anchor point for transportation of electrons? A better structure than metal@semiconductor.
You can reduce the surface defects with coating the nanoparticles but you should see what you gain out of it. If you are going to use your nanoparticles for solar cells, based on my humble knowledge, it would not give you any benefit if it does not hurt your efficiency. You may think to reduce scattering light and dielectric losses induced by surface defects in order to enhance the efficiency. But you should notice metals are much more conductive comparing to the semiconductors. It means the absorbed light is converted to heat much faster rather than being converted to generation of electron-hole pairs.
Having a semiconductor core and a metal shell definitely can change the properties. If you were working on cell separation or hyperthermia cancer treatment, I would say the nanoparticles with a metal shell can give you multitude benefits. You can enhance the plasmon surface effects while having bio-compatible nanopartices.
I think the p-type semiconductor for core may be more efficient to abrove metal SPR and formation of e-h pair .
Dear Anchal,
welcome,
If you shell the semiconductor nano particles with metals it may render it metal like rather semiconductor since the conduction will be affected by the metal sheath since metals have much better conductivity than the semiconductor core. Also , optically it may be much more reflective after coating it with metal.
A better way to enhance the nano grains is to enclose them with oxides such as SiO2 or Al2O3 or even transpernt metal oxides. The role of theses oxide is to passiivate the surface of the particles.
Best wishes
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