Dear Sir,
I have query regarding band gap measurement using Tauc's plot. I have synthesised a new perovskite material and have measured the absorbance. I have plotted the graph (αhν)^2 vs hν and measured the band gap . To check whether material has direct band gap or indirect band gap, I have plotted the graph (αhν)^2 vs hν and measured the band gap . And another graph (αhν)^0.5 vs hν is plotted. Both graph showing same type of curve but there is difference in band gap.
How to decide whether this material have direct band gap or indirect band gap if (αhν)^2 vs hν AND (αhν)^0.5 vs hν show same type of curve .
Dear Dr Abdelkader Hafdallah ,
Thanks for your suggestion. Article suggested by you is good but its not mentioning anything which can solve my problem .
The value of direct band gap is 2.95 eV, while indirect band gap is 3.1 eV.
Sometimes the scale factor on the y axis is important.
Could you send copies of the two plots?
You must try
ARPES measurements where one can easily map the band characteristics.
A material with direct bandgap will, by definition, ALWAYS have lots of indirect bandgaps that are higher - these are measuring transitions to other valleys in the conduction band. An indirect bandgap really means it should be lower than any direct one. Your measurements, however, show undulations below the extrapolated bandgaps, rather than noise. How have you measured these?
Thanks Dr Walther for giving your valuable time. The band gap calculated from UV- visible absorption measurement .
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