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Abstract:
Solar cells with CuInSe2 absorbers are among the most promising
thin-film technologies, but the role of defects is not yet understood.
Monte Carlo (MC) simulations based on density functional theory have
been employed to investigate the formation conditions and properties of
Cu-poor defect structures. We find that CuIn5Se8 undergoes a
discontinuous order-disorder phase transition below room temperature.
Grand-canonical MC simulations provide a map of stability regions for
CuInSe2, CuIn3Se5, CuIn5Se8, and other Cu-poor stoichiometries as a
function of the chemical potentials. The stability regions of CuIn3Se5
and CuIn5Se8 are greatly diminished at elevated temperatures. Altering
the chemical potentials can be mimicked in experiment by adjusting the
vapor pressure in a physical vapor deposition process.
