Bulk Cu2O has bandgap 2.2 ev. I have synthesized nano Cu2O. It's particle size is 38 nm. Since it is known from theory that bandgap of nanoparticle is greater than that of Bulk. But my sample has bandgap of 1.9 ev. which is even less than the bulk bandgap. What can be reason of this reduction in bandgap.
As I think, there are two options:
1) a lot of defects in your nanoparticles. Defects effect are dominating over quantum confinement effect.
2) perhaps you measured surface plasmon resonance band
As the size of the Cu2O particle decreases, the confinement of the electrons and holes becomes stronger. The energy difference between the valence band and conduction band becomes less, leading to a smaller bandgap. Therefore, the bandgap of Cu2O nanoparticles is smaller than that of bulk Cu2O.
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Sajjad Janfaza , Correct me if I'm wrong. Confinement of the electrons and holes become stronger, leading to a higher exciton binding energy. Consequently, band gap increases, doesn't it?
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