Cu(InGa)Se/sub 2/ thin films by elemental co-evaporation/sputtering and large area module results
We report process optimization and understanding resulting in high quality Cu(In,Ga)Se/sub 2/ (CIGS) films and high efficiency devices/modules using a hybrid process for CIGS formation. In the hybrid process, the Cu is supplied by magnetron sputtering, and the In, Ga, and Se are supplied by linear thermal sources. The advantages of the hybrid process include: i) the ease and precision of Cu thickness control; and ii) flexibility to adjust the Ga depth profile. The investigation was conducted in a large-area, pilot-line system. Among others, important parameters were found to be the Cu/(In+Ga) ratio of the Cu/(InGa)/sub 2/Se/sub 3/ precursor, selenization temperature, and timing of the Ga and In fluxes. Cell efficiencies of over 13.0% and module efficiencies of 7.5% (26 W, 0.35 m/sup 2/) were achieved. The film properties were investigated by XRD, SEM, and AES.
Structure, chemistry, and growth mechanisms of photovoltaic quality thin‐film Cu(In,Ga)Se2 grown from a mixed‐phase precursor
The formation chemistry and growth dynamics of thin‐film CuInSe2 grown by physical vapor deposition have been considered along the reaction path leading from the CuxSe:CuInSe2 two‐phase region to single‐phase CuInSe2. The (Cu2Se)β(CuInSe2)1−β (0<β≤1) mixed‐phase precursor is created in a manner consistent with a liquid‐phase assisted growth process. At substrate temperatures above 500 °C and in the presence of excess Se, the film structure is columnar through the film thickness with column diameters in the range of 2.0–5.0 μm. Films deposited on glass are described as highly oriented with nearly exclusive (112) crystalline orientation. CuInSe2:CuxSe phase separation is identified and occurs primarily normal to the substrate plane at free surfaces. Single‐phase CuInSe2 is created by the conversion of the CuxSe into CuInSe2 upon exposure to In and Se activity. Noninterrupted columnar growth continues at substrate temperatures above 500 °C. The addition of In in excess of that required for conversion produce...
PULSE: a high-repetition-rate linac driver for x-ray FELs
We describe a staged concept for a linac-based freeelectron laser providing coherent tuneable VUV and soft X-ray output with pulse lengths down to 10 fs or less. Use of 1.3 GHz cryomodules operated with CW RF will allow flexible pulse patterns at potentially very high repetition rates up to 1 MHz. We consider the options for FELs that may be included in a facility of this type.