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Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 68: Photovoltaics: Chalcopyrites II

HL 68.3: Talk

Thursday, March 17, 2011, 10:45–11:00, FOE Anorg

Ab initio based Monte Carlo studies of Cu-depleted CIS phases for solar cellsChristian Ludwig1, •Thomas Gruhn1, Claudia Felser1, and Johannes Windeln21Institut für Anorganische and Analytische Chemie, Johannes Gutenberg-Universität Mainz, Deutschland — 2IBM Mainz, Deutschland

Thin film solar cells with a CuInSe2 (CIS) absorber layer have an increasing share of the solar cell market because of their low production costs and the high efficiency. One interesting aspect of CIS is the inherent resilience to defects and composition fluctuations. Beside the stable CuInSe2 phase, there are various Cu-poor phases along the Cu2Se–In2Se3 tie line, including the CuIn3Se5 and the CuIn5Se8 phase.

We have used ab initio calculations of Cu-poor CIS configurations to make a cluster expansion of the configurational energy. In the configurations, Cu atoms, In atoms, and vacancies are distributed over the Cu and In sites of a CIS cell with fixed Se atoms. With the resulting energy expression, CuIn3Se5 and CuIn5Se8 systems have been studied in the canonical ensemble. By analyzing the free energy landscape the transition temperature between a low-temperature ordered and a high-temperature disordered CuIn5Se8 phase has been determined.

Furthermore, grandcanonical ensemble simulations have been carried out, which provide the equilibrium Cu and In concentrations as a function of the chemical potentials µCu and µIn. Plateau regions for the CuInSe2 and the CuIn5Se8 phases have been found and analyzed for different temperatures.

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