Stability of Cd1-xZnxOyS1-y Quaternary Alloys Assessed with First-Principles Calculations

Joel B Varley; Xiaoqing He; Angus Rockett; Vincenzo Lordi

doi:10.1021/acsami.6b14415

Stability of Cd_1-xZn_xO_yS_1-y Quaternary Alloys Assessed with First-Principles Calculations

ACS Appl Mater Interfaces. 2017 Feb 22;9(7):5673-5677. doi: 10.1021/acsami.6b14415. Epub 2017 Feb 9.

Authors

Joel B Varley¹, Xiaoqing He², Angus Rockett², Vincenzo Lordi¹

Affiliations

¹ Materials Science Division, Lawrence Livermore National Laboratory , Livermore, California 94550, United States.
² Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.

PMID: 28176522
DOI: 10.1021/acsami.6b14415

Abstract

One route to decreasing the absorption in CdS buffer layers in Cu(In,Ga)Se₂ and Cu₂ZnSn(S,Se)₄ thin-film photovoltaics is by alloying. Here we use first-principles calculations based on hybrid functionals to assess the energetics and stability of quaternary Cd, Zn, O, and S (Cd_1-xZn_xO_yS_1-y) alloys within a regular solution model. Our results identify that full miscibility of most Cd_1-xZn_xO_yS_1-y compositions and even binaries like Zn(O,S) is outside typical photovoltaic processing conditions. The results suggest that the tendency for phase separation of the oxysulfides may drive the nucleation of other phases such as sulfates that have been increasingly observed in oxygenated CdS and ZnS.

Keywords: CIGS; CZTS; alloy; buffer layer; density functional theory; thin-film photovoltaics.