Published online by Cambridge University Press: 21 March 2011
Cu(In,Ga)Se2 thin films were prepared by physical vapor deposition. The CIGS films were deposited by three kinds of method. The 1st was “2-stage process” in which (In,Ga)2Se3 precursor layer was deposited on Mo coated soda-lime glass at the 1st stage, and then exposed to Cu and Se fluxes to form CIGS films at the 2nd stage. The 2nd method was an ordinary “3-stage process”. The 3rd method was “2-stage deposition and post-annealing process” in which CIGS films were deposited at low substrate temperatures and then the obtained CIGS precursor films were annealed in Se flux at high temperatures. A solar cell using a CIGS film prepared at 400 °C by the “2-stage process” showed an efficiency of 11.8 % and that using a CIGS film deposited at 350 °C by the “3-stage process” showed an efficiency of 12.4 %. The CIGS films deposited by the “2-stage deposition and post-annealing process” have similar microstructures to the device quality CIGS films deposited by the “3-stage process” at high temperatures. The solar cell with an MgF2/ITO/ZnO/CdS/CIGS/Mo/glass structure showed an efficiency of 17.5 % (Voc=0.634 V, Jsc=36.4 mA/cm2, FF=0.756). The thin CIGS films with a smooth and flat surface can be fabricated by the “2-stage deposition and post-annealing process”. The solar cell using a 0.7μm CIGS absorber layer showed an efficiency of over 12 % and a large open circuit voltage of 0.677 V.
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