Growth of Cu2ZnSnS4 absorber layer on flexible metallic substrates for thin film solar cell applications

Abstract

In this work, Cu 2 ZnSnS 4 (CZTS) absorber layers were fabricated using a two-stage process. Sequentially deposited Cu-Zn-Sn thin film layers on metallic foils were annealed in an Ar + S 2(g) atmosphere. We aimed to investigate the role of flexible titanium and molybdenum foil substrates in the growth mechanism of CZTS thin films. The Raman spectra and X-ray photoelectron spectroscopy analyses of the sulfurized thin films revealed that, except for the presence of Sn-based secondary phases, nearly pure CZTS thin films were obtained. Additionally, the intense and sharp X-ray diffraction peak from the (112) plane provided evidence of good crystallinity. Electron dispersive spectroscopy analysis indicated sufficient sulfur content but poor Zn atomic weight percentage in the films. Absorption and band-gap energy analyses were carried out to confirm the suitability of CZTS thin films as the absorber layer in solar cell applications. Hall effect measurements showed the p-type semiconductor behavior of the CZTS samples. Moreover, the back contact behavior of these metallic flexible substrates was investigated and compared. We detected formation of cracks in the CZTS layer on the molybdenum foils, which indicates the incompatibility of molybdenum's thermal expansion coefficient with the CZTS structure. We demonstrated the application of the magnetron sputtering technique for the fabrication of CZTS thin films on titanium foils having lightweight, flexible properties and suitable for roll-to-roll manufacturing for high throughput fabrication. Titanium foils are also cost competitive compared to molybdenum foils.

Efficient (Cu1−xAgx)2ZnSn(S,Se)4 solar cells on flexible Mo foils

“…8 Compared with the rigid substrates, the exible substrates have the advantages of high temperature resistance, good mechanical strength, and a compatible coefcient of linear thermal expansion especially for Mo foil. [9][10][11][12] Due to cost-effective roll-to-roll processes, exible PV devices are more attractive for their potential applications in both ground and space. For CZTSSe devices based on either rigid glass substrates or exible substrates, the current bottleneck is the high V oc,def , which is due to the quantity of Cu Zn antisite acceptor defects and band tailing caused by Cu/Zn disorder.…”

Importance of CdS buffer layer thickness on Cu2ZnSnS4-based solar cell efficiency

“…For all the reasons mentioned above and others, CZTS might be an ideal candidate to produce thin film solar cells, which might replace CIGS in a decade's time. Various techniques such as evaporation [18], sputtering [19], pulsed laser deposition [20], chemical vapor deposition [21], spray pyrolysis [22], spincoating [23], and electrochemical deposition [24] have been reported for the growth of CZTS absorber films. Among these, the sputtering technique is extensively preferred due to the availability of the thickness control of the metallic precursor, the large area growth occurring at one time, and the reproducible fabrication.…”

Metal mesh filters based on Ti, ITO and Cu thin films for terahertz waves

“…Titanium and copper thin films were grown in high vacuum dc magnetron sputtering system on fused silica substrates by a system identical to ref. (Yazici et al 2015). We have deposited the films under identical growth conditions such as argon partial pressure, dc power and the deposition time.…”