Analyzing UV/Vis/NIR Spectra—Part II: Correct and Efficient Parameter Extraction

Exact optical analysis of transparent conducting oxide (TCO) and absorber layers are necessary to optimize adequate materials for thin-film solar cell applications. A nonnumerical theoretical concept has been developed to extract approximation-free optical and electrical data from ultraviolet/visible/near-infrared (UV/Vis/NIR) spectra. Special focus has been set on double-layer systems, as thin films upon substrates. Complex parameter evaluation is possible. Sputtered TCO and absorber thin films—aluminum-doped zinc-oxide and tin-sulphide—have been analyzed with respect to process-temperature
$T$
. Results were compared with those of the well-known Keradec/Swanepoel model. The necessity of taking both spectra—transmission and reflection spectra— into account has been shown. Results have been discussed with structural properties of the thin films with the help of X-ray diffraction measurements. A noncontact, optical conductivity measurement possibility by use of UV/Vis/NIR spectroscopy has been introduced. Optically measured conductivities
$\sigma_{L}$
were compared with those measured electrically with a four-tip measurement system.