BandGap Engineering

"DFT studies on Materials for Solar Energy Applications"

Solar energy is one of the largest sources of renewable energy received from the sun, which can be converted into electrical and thermal energy by suitable technology, using photovoltaic and thermoelectric materials, respectively. Understanding the fundamental properties of these materials is essential to enhance the conversion efficiency and thereby increase the utilization of solar energy. Developing the new class of solar cell materials and advancing their technological transformation are required for this purpose.

In past decades Transparent Conducting (TC) materials have been attractive, due to their unique combination of two contradictory properties, viz. transparency due to wide energy bandgap, and high electrical conductivity due to defects. TC materials are used in a wide range of applications such as solar cells, optoelectronic devices, optical sensors, light-emitting diodes, and flat panel displays etc. In solar cells, the TC materials are used as a window material due to their transparency that enables absorption of wide solar spectrum and also as electrical contacts due to their high electrical conductivity. From the past few decades, Oxide TC materials such as Tin Oxide (SnO2), Indium Oxide (In2O3), Indium doped Tin Oxide (ITO), and Zinc Oxide (ZnO), are dominating the technological world because of their high electrical conductivity and optical transparency.

We have started exploring TC Nitrides, as they are having wide and direct bandgaps, high carrier concentration, high electronic mobility, large bulk modulus, and cost-effective constituents. We have analyzed the electronic structure of A3N2 (A=Mg, Zn, and Sn) and Sn3N4.

We have also investigated one of the famous p-type TCO, CuYO2 and analysed its electronic structure under the influence of intrinsic defects like vacancies and Oxygen interstitials as well as co-doping of Oi with BY, AlY, GaY, and InY. Moreover, we have elucidated that intermediate bands that can enhance photon absorption can be introduced by doping CuYO2 with suitable combination of intrinsic defects and impurity atoms.

For example, we have shown that, by doping CuYO2 with Ni, Pi, and Asi at interstitial sites, an intermediate band is obtained above the valence band and is well separated from the conduction band, thereby enhancing the absorption of solar photons and increasing the solar energy conversion efficiency.

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Sir CV Raman Block , Anna University.



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