Methodological Investigation of the Band Gap Determination of Solid Semiconductors via UV/Vis Spectroscopy

Abstract

Several different evaluation methods (EM) to obtain the band gap energy (Eg) of semiconductors via UV/Vis diffuse reflectance spectroscopy (DRS) are used in literature and no clear consensus which EM to use is established. By using P25 as a model semiconductor, evaluating 32 literature sources and our own experiments, we show that the determined Eg energy is heavily influenced by the EM (differences in Eg of up to 0.87 eV). For P25 loaded with CuO even contradictive effects of metal loading on the Eg are observed using different EM. Different phase compositions of TiO2 are also shown to yield EM-dependent results. This paper thus comprehensively investigates the most common EM on different relevant photocatalyst material classes, illustrates their mathematical and graphical determination, gives recommendations which method to use based on a quantitative indicator and illustrates common pitfalls in determining Eg via UV/Vis DRS.