AVS 62nd International Symposium & Exhibition
    Energy Frontiers Focus Topic Monday Sessions
       Session EN+AS+EM+NS+SE+SS+TF-MoM

Paper EN+AS+EM+NS+SE+SS+TF-MoM1
Elevated Temperature Phase Stability of CZTS-Se Thin Films for Solar Cells

Monday, October 19, 2015, 8:20 am, Room 211B

Session: Solar Cells I
Presenter: Andrew C. Kummel, University of California at San Diego
Authors: E. Chagarov, University of California at San Diego
K. Sardashti, University of California at San Diego
D.B. Mitzi, Duke University
R.A. Haight, IBM T.J. Watson Research Center
A.C. Kummel, University of California at San Diego
Correspondent: Click to Email
Density-functional theory simulations of CZTS, CZTSe and CZTS0.25Se0.75 photovoltaic compounds have been performed to investigate stability of CZTS0.25Se0.75 alloy vs. decomposition to CZTS, CZTSe and other secondary compounds. The Gibbs energy for vibration contribution was estimated by calculating phonon spectra and thermodynamic properties at finite temperatures. It was demonstrated that CZTS0.25Se0.75 alloy is stabilized not by enthalpy of formation but by vibration and mixing contributions to the Gibbs energy. A set of phase diagrams was built in multidimensional space of chemical potentials at 300K and 900K temperatures to demonstrate alloy stability and boundary compounds at various chemical conditions. The Gibbs energy gain/loss for several decomposition reactions was calculated as a function of temperature with/without Cu/Zn intermixing and vibration contributions to the Gibbs energy demonstrating CZTS0.25Se0.75 that even defect-free (no Cu/Zn intermixing) CZTS0.25Se0.75 can be stable at typical processing temperatures.