Hi, I'm working in thinfilm solarcells.can anyone tell me how absorber layer deposited from nanoparticles are having better absorption than prepared from normal precursor materials?
There are lots of possibilities, but better absorption generally would imply either a change in the type of transition (indirect to direct) or an increase in the CB density of states. The first is more likely, there is a known indirect to direct transition in MoS2 when single layers are isolated (change to nano scale). Another possibility is simply better light trapping due to nano texturing. (increased scattering)
@Adam Welch: Thank you sir.but in the 2nd possibility ,if scattering of light increases how the absorption will be better?
In this case, scattering doesn't mean that the light will scatter out of the system. The scattered light will make the excitation of electron between p-type & n-type semiconductor layers and as electron move quickly, it will allow to absorb more light which will make your p-v system more efficient.
@Abdullah Ashraf: thank you sir.but still iam not very clear about ur statement .can you explain it .
If you give us more details about your setup, we can likely give more precise answers. In the case of scattering, the enhanced light absorption would only be an "effective" enhancement. Absorption theory assumes a flat, single crystal with minimal interfaces (one front, and one back). Once you increase the number of interfaces to the extent that a particle has just as much interface as it does bulk (a nanoparticle), then you have adjust the theory to accommodate. In this case, you have to account for the fact that the light will be scattered, reflected, and absorbed at every interface. Where scattering can be ignored for just two interfaces (standard theory), it is going to play a much larger role in nanoparticle absorption. This increased scattering leads to increased "off angle" incidence with subsequent particles (after reflection and scattering from the initial particle), and thus increased total internal reflection. Internal reflection increases the path length light travels within one particle, which increases effective absorption. Hope that explains it well.
- Badges
- Science topic