Berlin 2015 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 5: Photovoltaics: CIGS and related compounds
HL 5.6: Talk
Monday, March 16, 2015, 10:45–11:00, EW 202
First Principle Calculation on the Energetics of Na and K Incorporation in CuInSe2 and CuIn5Se8 — Elaheh Ghorbani1,2, •Janos Kiss3, Hossein Mirhosseini3, Thomas Kuehne4, and Claudia Felser3 — 1Johannes Gutenberg univesity, Mainz, Germany — 2IBM, Mainz, Germany — 3MPI for Chemical Physics of Solids, Dresden, Germany — 4University of Paderborn, Paderborn, Germany
In the present work we study sodium and potassium extrinsic defects incorporating into several substitutional and interstitial positions in CuInSe2 and CuIn5Se8 by means of theoretical density functional theory calculations (including some fraction of exact Hartree-Fock exchange). Our research reveals the most and least favorable sites for Na and K in the light absorber layer of CIGS-based thin film solar cells. We have also studied the energetics of dumbbells. Our calculations show: (i) Among substitutional positions, occupying a Cu position (by Na or K) takes much less energy than occupying an In or a Se position. (ii) Interstitial positions which are tetrahedrally coordinated by 2 Na and 2 In are more favourable for both Na and K than interstitial positions which are tetrahedrally coordinated by 4 Se atoms. (iii) All (Na-Na), (Na-K) and (K-K) dumbbells can form in CuInSe2 and CuIn5Se8. Among dumbbells (Na-Na) and (K-K) have the lowest and highest formation energies respectively. (iv) Dumbbells can occupy the pristine vacant copper position of CuIn5Se8, without creating new Cu-defects. (v)Our band structure results show which defects will cause the appearance of new defects states in the gap of absorber.