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.
New technologies for CIGS photovoltaics
Abstract This paper describes a new process for forming Cu(In,Ga)Se 2 (CIGS) by vacuum processing. It is termed the hybrid process, and it involves thermal delivery of In, Ga, and Se and sputtering of Cu. The optimization of the process is described, followed by its successful application to large area processing of CIGS devices and modules. Other processing issues in module formation are also discussed and analyzed, including deposition of the buffer and window layers, and interconnect resistance. The paper also describes the application of a new sputtering process for compound film formation to the area of CIGS processing. This process is termed reactive environment sputtering, and is based on a hollow cathode discharge. The process is applied to the formation of transparent conducting oxides (TCO) such as ZnO:Al, ZnO:B, In 2 O 3 :Mo (IMO) and In 2 O 3 :Ti (ITiO), and to their use as window layers for CIGS devices.
Recalculation of Mass Defects
THE well-known mass defect curve of the old nuclear scheme calculated with regard to α-particles and protons presented a difficulty with its minimum of binding energy for tin and an increasing portion between tin and lead. On the other hand, the mass defect values against protons give a rather smoothly decreasing curve.1 As has already been pointed out,2 the number of α-particles must be considerably reduced from the point of view of the new scheme, which does not admit any electrons in nuclei, but only neutrons and protons (presumably joined as α-particles). The curve of mass defect against protons and neutrons (perhaps with a single ‘central’ α-particle) is very similar to the old curve against protons, but decreases less rapidly. Clearly the new mass defect values relatively to α-particles, neutrons and protons must lie somewhere between the old values computed relative to protons and α-particles respectively (because the number of α-particles is decreased). We may emphasise that this new mass defect curve shows no increasing portion between tin and lead. For illustration we give two typical values: Old: 50Sn124 = 31α + 12&#38;epsiv;; mass defect = 0.158 (in mass units); 82Pb208 = 52α + 22&#38;epsiv;; mass defect = 0.035. New: 50Sn124= 25α + 24ω (ω = neutron); mass defect = 0.304; 82Pb208 = 41α + 44ω; mass defect = 0.366.