Issue 41, 2013

Real-time observation of Cu2ZnSn(S,Se)4 solar cell absorber layer formation from nanoparticle precursors

Abstract

The selenization of Cu–Zn–Sn–S nanocrystals is a promising route for the fabrication of low-cost thin film solar cells. However, the reaction pathway of this process is not completely understood. Here, the evolution of phase formation, grain size, and elemental distributions is investigated during the selenization of Cu–Zn–Sn–S nanoparticle precursor thin films by synchrotron-based in situ energy-dispersive X-ray diffraction and fluorescence analysis as well as by ex situ electron microscopy. The precursor films are heated in a closed volume inside a vacuum chamber in the presence of selenium vapor while diffraction and fluorescence signals are recorded. The presented results reveal that during the selenization the cations diffuse to the surface to form large grains on top of the nanoparticle layer and the selenization of the film takes place through two simultaneous reactions: (1) a direct and fast formation of large grained selenides, starting with copper selenide which is subsequently transformed into Cu2ZnSnSe4; and (2) a slower selenization of the remaining nanoparticles. As a consequence of the initial formation of copper selenides at the surface, the subsequent formation of CZTSe starts under Cu-rich conditions despite an overall Cu-poor composition of the film. The implications of this process path for the film quality are discussed. Additionally, the proposed growth model provides an explanation for the previously observed accumulation of carbon from the nanoparticle precursor beneath the large grained layer.

Graphical abstract: Real-time observation of Cu2ZnSn(S,Se)4 solar cell absorber layer formation from nanoparticle precursors

Supplementary files

Article information

Article type
Paper
Submitted
30 Apr 2013
Accepted
29 Aug 2013
First published
30 Aug 2013

Phys. Chem. Chem. Phys., 2013,15, 18281-18289

Real-time observation of Cu2ZnSn(S,Se)4 solar cell absorber layer formation from nanoparticle precursors

R. Mainz, B. C. Walker, S. S. Schmidt, O. Zander, A. Weber, H. Rodriguez-Alvarez, J. Just, M. Klaus, R. Agrawal and T. Unold, Phys. Chem. Chem. Phys., 2013, 15, 18281 DOI: 10.1039/C3CP53373E

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