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HL: Fachverband Halbleiterphysik

HL 8: Photovoltaics

HL 8.8: Vortrag

Montag, 20. März 2017, 11:30–11:45, POT 251

Many-body effects in X-ray absorption spectra of the sulfur L_2,3 edge in Cu₂ZnSnS₄ — •Archana Manoharan¹, Lorenzo Pardini¹, and Claudia Draxl^1,2 — ¹Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, Germany — ²European Theoretical Spectroscopic Facility (ETSF)

The kesterite material Cu₂ZnSnS₄ (CZTS) is a promising candidate as an absorber layer for solar-cell applications. In the present work, we study its structural, electronic, and X-ray absorption properties using a first-principles approach. We explore the X-ray absorption spectra at the sulfur L_2,3 edge in CZTS by solving the Bethe-Salpeter equation (BSE) and compare them to corresponding binary phases, i.e., ZnS and SnS₂. Special emphasis is put on the spin-orbit coupling between the S 2p_1/2 and 2p_3/2 core states. In comparison to the independent-particle approximation, the inclusion of Coulomb interaction redshifts the absorption edge in all three materials. In case of CZTS, a bound exciton is found. It is formed by transition from the S 2p_3/2 core state. The second peak with excitonic character is due to the mixing of excitation channels of the L₂ and L₃ edges. In the binary phases, a bound state is observed in SnS₂ but not in ZnS. We assign the bound exciton in CZTS to hybridisation of Sn with S. The calculated BSE results are in good agreement with experimental spectra.