Comparative study of sputtered and electrodeposited CI(S,Se) and CIGSe thin films
Introduction
Because of their high absorption coefficient of sun light and their high tolerance to the presence of defects (grain boundaries, vacancies, interstitials…), ternary chalcopyrite, CI(S,Se) and their alloys with gallium CIG(S,Se) are becoming among the leading candidates for high efficiency and low-cost terrestrial photovoltaic devices. Indeed, polycrystalline CI(S,Se) and CIG(S,Se) based solar cells have achieved efficiencies of about 19% on a laboratory scale [1], [2], [3] and around 14% for modules [4]. Furthermore, the cells have shown very good outdoor stability and resistance to radiations [5]. CI(S,Se) and CIG(S,Se) thin films have been prepared using a variety of processes including coevaporation of the elements in different ways [3], [6], [7], [8], two or three stage process consisting in sequentially sputtered Cu and In thin layers and a subsequent chalcogenisation by selenisation [9], [10], and electrodeposition [11], [12], [13]. The properties of the grown layers seem to be dependent on the preparation technique. The best results were obtained by the coevaporation process [3]. However, it is difficult in upscaling and involves high vacuum and thus high cost. Though electrodeposition has led to the preparation of conversion structures with efficiency less than its counterpart vacuum techniques, it is a very attractive technique because it is cost effective and suitable for large area modules and thus constitutes a possible alternative to decrease the production costs of CI(S,Se) and CIG(S,Se) modules. Finally, CdS was the buffer layer currently used in chalcopyrite based solar cells. However, Cadmium is a heavy metal and should be avoided. Alternative buffer layers were developed such as Zn(X,O) (X = S, Se) [14], [15], In(OH,S) [16], ZnS [17], In2S3 [18], [19]. Such a reduction of environmental impact will significantly foster the development of CI(S,Se) technology. The present contribution deals with a comparative study of structural, optical and electrical properties of CIS, CISe and CIGSe thin films grown by both a vacuum and a non-vacuum method. A two-stage growth process consisting on a sequential deposition by sputtering of Cu and In layers on Mo coated glass and a subsequent sulfurisation of this multilayer structure in vacuum partial pressure, and a non-vacuum process consisting in one step electrodeposition of the elements.
Section snippets
Preparation of CuInS2 (CIS) films
Cu–In metallic precursor multilayers were obtained by rf sputtering technique. Sequential deposition of Cu and In were performed on Mo coated glass substrates. Altogether 20 alternate layers were obtained under a 2 × 10− 5 Torr partial argon pressure. The thickness of the samples was varied by increasing the deposition time from 5 to 20 min per layer. All the samples were subsequently annealed at temperatures scaling from 160 to 400 °C for 2 h in vacuum (10− 3 Torr). The samples were inserted then
Sulfurised Cu–In multilayers
In order to understand the sulfurisation mechanism of our Cu–In multilayers with the annealing temperature, XRD analyses were performed to identify the formation of different phases. Fig. 1 shows the XRD spectra of Cu–In multilayers before sulfurisation. Cu and Cu–In alloy (CuIn2) are detected but indium cannot be observed. The formation of CuIn2 compound during the deposition was reported by other authors [9], [22]. Annealing at 160, 250 and 400 °C lead to the formation of the Cu11In9 phase
Conclusion
CI(S,Se) and CIGSe thin films were successfully prepared by both a vacuum and a non-vacuum methods. All the films crystallize in the well known chalcopyrite structure with the preferential orientation in the (112) plane. The most important conclusion pointed out after this study is that electrodeposition is an interesting and cost effective technique for the preparation of good quality CISe and CIGSe films. The Ga grading could be performed by the simple addition of gallium precursor in the
Acknowledgments
This work was partially supported by the CNRST/CNRS cooperation program (Chimie 05/06).
References (27)
- et al.
Sol. Energy Mater. Sol. Cells
(1998) - et al.
Sol. Energy Mater. Sol. Cells
(2001) - et al.
Thin Solid Films
(2005) - et al.
Thin Solid Films
(2005) - et al.
Sol. Energy
(2004) - et al.
Thin Solid Films
(2003) - et al.
Sol. Energy Mater. Sol. Cells
(2001) - et al.
Thin Solid Films
(2003) - et al.
Thin Solid Films
(1996) - et al.
Thin Solid Films
(1996)
Sol. Energy Mater. Sol. Cells
Prog. Photovolt. Res. Appl.
Prog. Photovolt. Res. Appl.
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