Dresden 2011 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 68: Photovoltaics: Chalcopyrites II

HL 68.3: Vortrag

Donnerstag, 17. März 2011, 10:45–11:00, FOE Anorg

Ab initio based Monte Carlo studies of Cu-depleted CIS phases for solar cells — Christian Ludwig¹, •Thomas Gruhn¹, Claudia Felser¹, and Johannes Windeln² — ¹Institut 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 µ_Cu and µ_In. Plateau regions for the CuInSe₂ and the CuIn₅Se₈ phases have been found and analyzed for different temperatures.