What this workflow helps you do
Estimate an optical band gap from UV–Vis data with a Tauc plot while keeping the signal transformation, transition model and fitted linear region visible. NotyPlot supports absorbance, transmittance, absorption-coefficient and diffuse-reflectance inputs, with optional thickness where conversion requires it.
Use this workflow when
- Estimating an optical band gap from UV–Vis absorption-related data.
- Comparing Tauc estimates across similarly prepared samples.
- Testing how the chosen transition model and fit window affect the extrapolated intercept.
What you need before you start
- UV–Vis data with a known wavelength or photon-energy axis and known signal type.
- Optical thickness when needed to convert absorbance or transmittance into an absorption coefficient.
- A justified transition model: direct/indirect and allowed/forbidden as appropriate to the material.
Step-by-step workflow
- Import the UV–Vis dataset and confirm the spectral axis, units and signal representation.
- Select or verify the Tauc signal type; enter optical thickness when it is required for the chosen conversion.
- Choose the transition model to define the Tauc exponent.
- Run the band-gap analysis and inspect the transformed Tauc plot, automatic fit window and R².
- Adjust the linear fit range when the automatic window includes curvature, noise or unrelated transitions.
- Report the extrapolated band gap together with signal transformation, transition assumption and fitted energy range.
What to review in the result
- The signal transformation is appropriate to the available UV–Vis measurement.
- The selected region is reasonably linear rather than chosen only to maximize R².
- The extrapolation to the energy axis is visually consistent with the fitted edge.
- Changing the fit window does not cause an unexplained large shift in the result.
Before you report or export
- Record the transition model and fit range.
- State how absorbance, transmittance or reflectance was converted for Tauc analysis.
- Compare samples using the same justified method rather than changing the model to obtain a preferred value.
Limitations and interpretation
- Tauc analysis is model-dependent and can be ambiguous for disordered, indirect, multi-transition or strongly scattering materials.
- Diffuse reflectance may require an appropriate transform and assumptions distinct from transmission measurements.
- A high R² alone does not prove that the selected region represents the correct absorption edge.