**UV Vis spectroscopy band gap calculation**

**Calculation Tutorial:**

**STEP1:** Open the absorption graph of the material, which is obtained from the UV Vis spectroscopy.

**STEP2: **Now zoom on the area for which you want to calculate the band gap and note down the wavelength (λ) at which absorption peak is shown.

**STEP3: **Now enter the measured wavelength value (eg. 31.8) into the ” Wavelength of Absorption peak (in nanometer)” column of the calculator. You should get the calculated results of the band gap in the “Calculated Result” field.

**Theory Behind Calculations:**

- UV Vis Spectroscopy absorption peak means the Electrons are absorbing the Energy at some specific wavelength.
- Electrons are absorbing Energy means the Electrons are going to excited state from its ground state.
- Electrons are going to excited state from its ground state means the material is having band gap, thus which can be determine by absorption wavelength.

**Energy Equation of Quantum Mechanics:**

Energy (E) = Planks Constant (h) * Speed of Light (C) / Wavelength (λ)

Where, Energy (E) = Band gap, Planks constant (h) = 6.626×10^-34 Joules sec, Velocity of Light (C) = 2.99×10^8 meter/sec and Wavelength (λ) = Absorption peak value. Also 1eV = 1.6×10^-19 Joules (Conversion factor)

By this formula band gap can be calculated easily, from UV Vis spectroscopy absorption peak.

## 5 Comments. Leave new

This is the useful and usual formula used to calculate the energy gap from the absorption spectra in the visible and ultraviolet regions and infrared region as well. This calculator which is given here will help the researcher to find directly the energy gap Eg.

What if my sample has two absorption peaks or no peak at all? How do I calculate my bandgap?

How to calculate urbach energy from band gap.

how to calculate band gap from tauc equation,what is the value of A?

Please note, that you should decide whether to use the use the peak maxima or the point where the peak begins. If you use the red edge of the absorption band (in the example maybe 250 nm), this might be a better result. DOI: 10.1039/C5SM00463B