http://www.cnr.it/ontology/cnr/individuo/prodotto/ID297083
Spectrophotometric methods for the determination of the band gap energy of materials for Dye-Sensitized Solar Cells (Contributo in atti di convegno)
- Type
- Label
- Spectrophotometric methods for the determination of the band gap energy of materials for Dye-Sensitized Solar Cells (Contributo in atti di convegno) (literal)
- Anno
- 2013-01-01T00:00:00+01:00 (literal)
- Alternative label
N. Sangiorgi, R. Bendoni, A. Sangirogi, A. Sanson (2013)
Spectrophotometric methods for the determination of the band gap energy of materials for Dye-Sensitized Solar Cells
in 4th Hybrid and Organic Photovoltaic Conference, Seville, Spain, 5-8 Maggio 2013
(literal)
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
- N. Sangiorgi, R. Bendoni, A. Sangirogi, A. Sanson (literal)
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
- Titolo
- Spectrophotometric methods for the determination of the band gap energy of materials for Dye-Sensitized Solar Cells (literal)
- Abstract
- The energy band gap (Eg) is one of the properties of a semiconductor material that
determines its possible application in energy devices such as Dye-Sensitized Solar Cells. There
are several methods for Eg determination, such as XPS, UPS, PL and optical spectroscopy. One
simple way is given by UV-Vis absorption spectroscopy on powder in suspension. Although
simple, this technique is strongly dependent on the suspension stability: the precipitation of
the powder can in fact affect the measurement leading to incorrect results. In order to avoid
these complications, diffuse reflectance spectroscopy can be considered as a valid alternative.
The aim of this work was to develop an easy and accurate method for Eg determination for
powder materials through the combination of diffuse reflectance spectroscopy and graphical
methods. The Eg determination through diffuse reflectance is possible using the Kubelka-Munk
equation (K-M) generally indicated as F(R) = (1-R)2/2R (where R is diffuse reflectance). In
literature several different methods have been used to graphically determine Eg from this
equation, without obtaining a unified and conclusive approach. For this reason in this work the
different approaches were tested and verified on well know TiO2 semiconductor in order to
assess the easiest and most reliable one. This was found to be the one that takes into account
the electronic transitions that occurs inside the semiconductor material (Tauc equation). The
method consists in combining the F(R) of the K-M equation with the one obtained applying the
Tauc equation in the equation ahv= A (hv-Eg)n where hv is the photon energy, A is a constant
and n is proportional to the electronic transition considered. In a material with a perfect
diffuse scattering the F(R) value becomes equal to the absorption coefficient (a). Although very
simple, this method required the knowledge of the correct value of the \"n\" exponent and it is
therefore necessary to establish the most convenient method for its determination. The n
value was here calculated through a suitable graphical method and the band gap value was
extrapolated by plotting (F(R)hv)1/n versus hv at (F(R)hv)1/n equal to zero. This approach
provided an accurate Eg value for the semiconductor model and was validated on other
common systems (e.g ZnO) showing good agreement with literature. (literal)
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