Title

Chemical Structure of a Carbon-Rich Layer at the Wet-Chemical Processed Cultformulatext_{2}formulaZnSn(S,Se)formulatext_{4}ltformulagtx002FMo Interface

Document Type

Article

Publication Date

5-1-2021

Publication Title

IEEE Journal of Photovoltaics

Volume

11

Issue

3

Abstract

The carbon-rich layer at the back-contact interface of a solution-processed Cu$_{2}$ZnSn(S,Se)$_{4}$ (CZTSSe) absorber is investigated with a combination of surface-sensitive X-ray photoelectron and bulk-sensitive X-ray emission spectroscopy. For absorber deposition, an aqueous ammonium-thioglycolate (ATGL) solution was used, and the “buried” back-contact interface was accessed by cleaving in a liquid nitrogen environment. In the pertinent literature, it is reported that such a carbon layer at the absorber/back-contact interface could have beneficial effects, e.g., to reduce series resistance or increase the short circuit current. Here, a detailed picture of the chemical structure of this carbon-rich layer at the back contact is derived, which consists of carbon (74 ± 7%), selenium (19 ± 4%), and sulfur (7 ± 3%). The selenium in this layer is found as elemental inclusions, possibly from not fully reacted selenium during the absorber production. The sulfur content in this carbon-rich layer is twice that of sulfur in the absorber. A detailed analysis of the chemical environment suggests that residuals from the aqueous ATGL solution are the origin of sulfur in this carbon-rich layer. Furthermore, underneath the carbon-rich layer, S-Mo bonds are found at the Mo back contact.

Keywords

Atmospheric measurements; Back contact; Carbon; Chemical structure; Kesterite; Light sources; Photoelectron spectroscopy; Photovoltaic cells; Spectroscopy; Sulfur; Thin-film solar cell; Wet-chemical processing; X-ray emission spectroscopy (XES); Xenon

Disciplines

Organic Chemistry

Language

English

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