Junction formation by Zn(O,S) sputtering yields CIGSe-based cells with efficiencies exceeding 18%

Abstract

In an effort to reduce the complexity and associated production costs of Cu(In,Ga)Se 2 (CIGSe)-based solar cells, the commonly used sputtered undoped ZnO layer has been modified to eliminate the requirement for a dedicated buffer layer. After replacing the ZnO target with a mixed ZnO/ZnS target, efficient solar cells could be prepared by sputtering directly onto the as-grown CIGSe surface. This approach has now been tested with high-quality lab-scale glass/Mo/CIGSe substrates. An efficiency of 18.3% has been independently confirmed without any post-deposition annealing or light soaking.

Study of Zn(O,S) films grown by aerosol assisted chemical vapour deposition and their application as buffer layers in Cu(In,Ga)(S,Se)2 solar cells

“…The best efficiencies for solar cells with sputtered or ALD deposited Zn(O,S) buffer layer are similar, 18.3% and 18.5% respectively (Klenk et al, 2013;Zimmermann et al, 2006). At the moment, the highest reported CBD deposited Zn(O,S) buffered solar cell efficiency is 20.9% (Kushiya, 2014).…”

“…So far, Zn(O,S) layers have been prepared by methods that are either slow, not in-line suitable or vacuum techniques, such as chemical bath deposition (CBD) (Buffière et al, 2011;Kushiya, 2004;Sáez-Araoz et al, 2008;Witte et al, 2013), atomic layer deposition (ALD) l t erjorkm n et l l t er-j rkm n et l., 2006; Sanders and Kitai, 1992;Zimmermann et al, 2006), sputtering (Grimm et al, 2011(Grimm et al, , 2010Klenk et al, 2013;Kobayashi et al, 2013;Nakamura et al, 2013). The best efficiencies for solar cells with sputtered or ALD deposited Zn(O,S) buffer layer are similar, 18.3% and 18.5% respectively (Klenk et al, 2013;Zimmermann et al, 2006).…”

Raman scattering quantitative assessment of the anion composition ratio in Zn(O,S) layers for Cd-free chalcogenide-based solar cells

“…Among the different alternatives to CdS, Zn(O,S) alloys have been reported as one of the most promising candidates, and high efficiency devices up to 21% efficiency have already been reported with these layers. [3][4][5][6][7] In this case, control of the O/S content ratio is very important in order to ensure an optimal moderate spike-like conduction band alignment at the absorber/buffer heterojunction. 8 However, the analysis of the anion ratio of these buffer layers by non-destructive techniques is still challenging, being the use of techniques as X-ray uo-rescence or X-ray diffraction compromised by either the presence of interactions between the S and Mo signals (being the back contact in the cells constituted by a Mo thin lm) or their very small thickness (typically in the range 20-80 nm).…”

Design, preparation and performance of Cu(In, Ga)(S, Se)<inf>2</inf>/Zn(O, S)/ZnO:Al solar cells

“…While some modifications to the process or cell stack may be required depending on the absorber type, the general finding is that sputtered Zn(O,S) works with sequentially processed and multi-source evaporated absorbers, wide-gap Cu(In,Ga)S2 and kesterite absorbers. In particular, an efficiency of 18.3% (with AR, confirmed) could be achieved with multi-source evaporated lab-scale absorber [6] without surface conditioning, annealing or light-soaking. …”