Cu2ZnSn(S,Se)4 photovoltaic absorber fabrication by hydride chalcogenization of electrodeposited precursors

Cu2ZnSn(S,Se)4 (CZTSSe) is a semiconducting material with potential application as the absorber layer in thin-film photovoltaic (PV) devices. Closely related to the commercially available Cu(In,Ga)Se2 (CIGS) absorber material, CZTSSe consists of more readily-available materials, and may therefore offer cost reduction and highly scalable production potential if its PV properties can be controlled and improved. This work presents a two-step process for fabricating CZTSSe: the metals Cu, Zn, and Sn are electrodeposited on a suitable conducting back-contact material, and then the resulting films are reacted under hydride gases, providing selenium and/or sulfur to form the final films. Two methods of electrodeposition are presented. First, a sequential bi-layer strategy deposits Cu-Sn alloy on the substrate, followed by a Cu-Zn layer on top of the Cu-Sn. This method presents extreme difficulties with poor adhesion of themetals, so an alternate method was developed in which the three metals are simultaneously co-deposited from the same electrolyte solution. Reaction of the metal precursors in hydrogen sulfide (H2S) and/or hydrogen selenide (H2Se) yields the quaternary films Cu2ZnSnS4 (CZTS), Cu2ZnSnSe4 (CZTSe), or CZTSSe, usually alongside a number of secondary phases. The effects of reaction conditions are studied to gain insight into the kinetic and thermodynamic properties of the reaction, which also enhances understanding of the presence of secondary phases in the reacted films. Prior to this work, the value of Gibbs free energy of formation for CZTSe had been unreported. Herein, empirical results from simultaneous H2S/H2Se reaction are combined with an estimate by Scragg [3] for the Gibbs free energy of formation of CZTS to estimate that of CZTSe. The new estimate for ΔG-formation of CZTSe indicates that the reaction is not strongly driven toward the quaternary, a finding which is confirmed by the secondary phases remaining after the reaction has completed.

Grantor dc:publisher

University of Delaware

Year dc:date.issued

2015

Author dc:creator

• Mangan, Thomas Christopher

DOI

https://doi.org/10.58088/3r74-ha80

OAI identifier oai:identifier

oai:udspace.udel.edu:19716/17583