I prepared semiconductor nanoparticles, but the problem I face is in the high absorption, which have a sharp rise. When I use it in tauc analysis to get band gap i have a big shift in the band gap.
What is the problem? The band gap can be obtained in a straight-forward way (http://www2.shimadzu.com/applications/UV/VIS/A428.pdf). As you can see, TAUC measurements produce results similar those obtained with diffuse reflectance measurements. You can use both methods to draw conclusions.
As one of the possible options, place the sample in a calibrated integrating sphere. This will allow you to take into account the scattered radiation with subsequent measurements.