Optical monitoring and control of three-stage coevaporated Cu(In1−xGax)Se2 by real-time spectroscopic ellipsometry
Real-time spectroscopic ellipsometry (RTSE) has been applied for in situ monitoring and control of thin-film copper-indium-gallium-diselenide, i.e., Cu(In1−xGax)Se2 (CIGS), deposition by high vacuum coevaporation in the three-stage process used for efficient photovoltaic devices. Initial studies have been performed on a ∼0.7-µm CIGS layer deposited on crystal silicon to minimize surface roughness and to develop an accurate structural/ optical model of the Cu-poor-to-Cu-rich and Cu-rich-to-Cu-poor transitions that define the ends of the second (II) and third (III) stages of growth, respectively.With a better understanding of the surface achieved through this model, correlations can be made between the surface state and the unprocessed RTSE data {ψ(t), Δ(t)}. During deposition in the solar cell configuration with 2- µm-thick CIGS on a Mo-coated glass substrate, indications of the Cu poor-to-rich and Cu rich-to-poor transitions appear clearly in {ψ(t), Δ(t)}, enabling direct control of stage II and III transitions. The transition times deduced optically are in good agreement with those identified from the film/substrate emissivity by tracking the substrate heater power. It is clear, however, that RTSE can provide higher sensitivity to these transitions and is, therefore, suitable for improved control of three-stage CIGS deposition.
In-situ and ex-situ characterizations of CIGS solar cells with KF post deposition treatment
In-Situ and ex-situ characterization were used to assess the effect of post deposition potassium fluoride treatment (KF PDT) on CIGS films and solar cells. Real time spectroscopic ellipsometry (RTSE) allowed observing in-situ the modification of the CIGS reflectance spectra during KF PDT. Next, deep-level transient spectroscopy (DLTS) and deep level optical spectroscopy (DLOS) allowed the identification of trap levels throughout the bandgap of CIGS film. Furthermore, scanning-DLTS was used to map spatial distribution of the observed traps.
Metallurgical Process Engineering
The "material of choice" - steel.- Uprising of China's steel industry.- Process manufacturing industry and process engineering.- Engineering science in steel manufacturing process.- Analysis and integration of metallurgical manufacturing process.- Multi-dimensional mass flow control for metallurgical manufacturing process.- Time factors in steel manufacturing process.-Operating dynamics in the production process of steel plant.- Structure and mode of steel plant.- Steel plant and environment.