The sun is one of the clean and sustainable energy source of the known universe. A solar cell application is mainly based on converting the photon energy to electrical energy which can be used in many other areas. Copper ternary chalcogenide based solar cells became a recent solution to the high cost problem of solar cells. Copper Indium diselenide solar cells as it appears from the name has an architecture of several layers which are sorted by CIGS (copper indium gallium selenide) as absorber layer, CdS (cadmium sulfide) as buffer layer, ZnO (zinc oxide) and ITO (Indium Tin Oxide) layers as window layer and top contacts for the device. With the recent laboratory scale improvements, the efficiency of CIGS solar cells rose to 19.9 % by NREL. One of the current research areas is based on sustaining the same efficiency on a bigger scale. In this work, the CIGS layer is deposited on Mo sputtered four inch soda-lime glass substrates. CIGS deposition step is done by physical vapor deposition of elemental species in an ultra-high vacuum system. CdS is deposited using chemical bath deposition. Top window layers ZnO, ITO and Ni/Al are sputter deposited. In this work we are attempting to develop a wide band-gap absorber material based on CIGS with low trap density and good interface lattice matching. We have done some preliminary investigation on Al doped CIGS films to see the effect on the optical band gap. Al doped CIGS devices will be fabricated to investigate the effect of Al doping on trap density.
Nagaich, Kush; Campbell, Stephen A..
Wide band gap CIGS based absorber for photovoltaic application.
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