Development of large scale CIGS solar panel using sputtering stacked multi-layer metallic precursor
Mo/CuGa/In (a) Mo/CuGa/In/CuGa/In/CuGa/In/CuGa/In/CuGa/In (b)
Mo/CuGa/In/In/ CuGa/ In/In/ CuGa/ In/ CuGa/ CuGa (c)
The bi-layer structure of molybdenum back contact was deposited under higher working pressure and lower working pressure respectively. The one depositing at higher working pressure had good adhesion, and the other had low resistivity. Mo film with bi-layer structure had a low resistivity 2.4x10-5Ω-cm. Commonly method of precursor preparation was sputter-deposition bilayer stucture Mo/CuGa/In (a) precursor by selenization., however, the bilayer precursor after selenization were rough of morphology. Therefore, the following stack was uncompletly covered. Multi-layer stacked-precursors, however , substituted that due to smooth surface of CIGS . Mo/CuGa/In/CuGa/In/CuGa/In/CuGa/In/CuGa/In (b), There was immediately following an idea about Ga profile, which was induced by changing the Ga concentration on the surface/bottom of CIGS film. CIGS by selenization normally introduced back surface field(BSF) , which is located at the backside between CIGS film and Mo back due to MoSe2 layer formed. On the other hand, a single grading band gap was established in CIGS cells, which attached previous world record efficiency 18.8%. It increased the collection efficiency of minor carriers, electron, but reduced the absorption of low energy photons resulting from broaden band gap at the backside of CIGS. Moreover, a lot of studies indicated that double grading was a promising profile to further increase the device performance. In this study, Ga profile fabrication was to potentiate double-grading energy band gap of CIGS. Mo/CuGa/In/In/ CuGa/ In/In/ CuGa/ In/ CuGa/ CuGa (c) Additionally, the prospective idea, multi-precursor stacked, was a favorable method for improving cell efficiency.