Manufacturing technology of CIGS (CuInGaSe2) thin film solar cells was investigated in Research Institute for Technical Physics and Materials Science of Hungarian Academy of Sciences. Efficiency of CIGS solar cells will be probably near to efficiency of Si ones but production costs are much lower because of small material consumption. To obtain high efficiency deposition of a puffer layer between the transparent ZnO contact layer and CIGS semi-conductor layer is necessary. One of possible materials for puffer layer is CdS but deposition of CdS is not vacuum-compatible. That is why instead of CdS use of ALD ZnO was investigated.
In my experimental work Al doped ZnO thin films with various Al/Zn composition ratios were deposited on Si and glass substrates by atomic layer deposition (ALD) at 150oC and effects of Al doping on ZnO films were analyzed. Room temperature resistivity of the AlZnO thin films was measured by van der Pauw measurements. The AlZnO films with Al content of up to 15 at% showed higher conductivity than intrinsic ZnO films. EDS measurements showed increasing Al mass percent in ZnO thin films in case of increasing number of Al precursor pulse during ALD. The crystal structure of AlZnO thin films was characterized by X-ray diffraction. XRD spectra show that Al-doped ZnO films have various preferred crystal orientation depending on Al at%. Thickness and refractive index of AlZnO thin films were measured by spectral ellipsometry measurements. Ellipsometry measurements showed decreasing refractive index of AlZnO in case of increasing Al at% and plotting of that was a linear curve.