Hi Yusuf,

Your plot suggests that the material has broad spectral absorption range. However, the plot doesn't show the beginning of the peak (which happens at higher wavelength), which indirectly suggests your bandgap (1240/λ, nm). As you have measured absorbance (A), you can use Tauc's plot to determine bandgap. i. e. use (Ahν)^n vs. hν plot. n = 1/2 or 2 depending on the nature of bandgap (direct or indirect).

Hope this helps.

Regards,

Sreekanth

Find reflectance and then use kubelka munk model for band gap calculation.

Hi Yusuf,

Your plot suggests that the material has broad spectral absorption range. However, the plot doesn't show the beginning of the peak (which happens at higher wavelength), which indirectly suggests your bandgap (1240/λ, nm). As you have measured absorbance (A), you can use Tauc's plot to determine bandgap. i. e. use (Ahν)^n vs. hν plot. n = 1/2 or 2 depending on the nature of bandgap (direct or indirect).

Hope this helps.

Regards,

Sreekanth

By using the following formula you calculate the band-gap of material from UV spectrum

Ebg = 1240/λ (eV)

Ebg = band-gap energy (eV)

λ = absorption maximum wavelength (nm) (Observed from UV-Vis Spectrum)

I agree with Omed. However, the incorporation of thickness only changes the numerical values of the plot but not the shape. If the thickness of the film is not known, one can directly go with absorbance to determine bandgap. If one has to calculate absorption coefficient, thickness is must.

Regards,

Sreekanth

Try a Tauc plot

http://en.wikipedia.org/wiki/Tauc_plot

You can make a Tauc plot from the absorbance data and calculate the bandgap.

I also see the more accurate Eg is obtained from Tauc plot.

Use Tauc plot. You have absorbance value. In (hv(a)), hv is maximum absorbance. In your case it is around 550 nm calculate the corresponding hv. That will be a constant and then multiply the absorbance value with this constant. Now you have (hv(a)) which is y-axis. Then convert the x-axis to photon energy using the formula,

E (eV) = 1240/wavelength (nm). Plot now and extend the slope to x-axis to get the band gap.

See book (optical process in semiconductor by pankove)

Here you can find good explanation and band gap calculator,

http://www.instanano.com/characterization/theoretical/uv-vis-spectroscopy-band-gap-calculation/

pls see the file for the determination of band gap