Band gap (Eg) calculation of UV-Vis spectroscopy from absorption spectra

Thin films band gap calculation for direct band gap semiconductor using origin and excel.
Tauch relation is solved for getting the required value.
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Detail description

First, collect the absorbance spectrum of your material using UV-Vis spectroscopy. This spectrum shows how much light the material absorbs at different wavelengths of the UV and visible light spectrum. The horizontal axis represents the wavelength of the light, while the vertical axis shows the absorbance.

2. Convert Wavelength to Energy
If your data is in terms of wavelength (which is often the case), you'll need to convert these values to energy. The relationship between the wavelength of light and its energy is inverse—shorter wavelengths correspond to higher energies. You can convert wavelength into energy using a formula based on physical constants like the speed of light and Planck's constant. This will allow you to express the absorbance data in terms of photon energy instead of wavelength.

3. Construct a Tauc Plot
To estimate the band gap, you can create what is known as a "Tauc plot." This method is commonly used to analyze materials' optical properties and estimate their band gap. You need to plot the photon energy on the horizontal axis, and on the vertical axis, plot a value related to the absorbance (this depends on whether the material has a direct or indirect band gap).

The idea here is that the absorbance starts to increase as the photon energy gets close to the band gap. Beyond this point, the relationship between absorbance and energy becomes more linear, which allows us to analyze the data.

4. Estimate the Band Gap Energy
Once the Tauc plot is created, focus on the linear portion of the graph where absorbance begins to increase. Extend this straight-line portion until it intersects the horizontal axis (energy axis). The point where it touches the axis gives you the band gap energy. This is the minimum energy required for the material to absorb light and move electrons from the valence band to the conduction band, which defines the band gap.

Summary
In summary, to calculate the band gap from UV-Vis spectroscopy:

Collect the absorbance spectrum.
Convert wavelength data into energy data.
Use the absorbance and energy data to construct a Tauc plot.
From the plot, determine the band gap by identifying where the absorbance data intersects the energy axis. This intersection point gives the energy value corresponding to the band gap.



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