SKM 2023 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 25: Perovskite and photovoltaics II (joint session HL/CPP)
HL 25.4: Talk
Wednesday, March 29, 2023, 10:30–10:45, JAN 0027
Interdiffusion of Cu(In,Ga)Se2 and Ag(In,Ga)Se2 investigated by In-Situ X-Ray Diffraction — •Julia Horstmann1, Roland Mainz2, Karsten Albe3, Heiko Kempa1, Torsten Hölscher1, and Roland Scheer1 — 1Martin-Luther-Universität Halle-Wittenberg, Germany — 2Helmholtz-Zentrum Berlin, Germany — 3Technische Universität Darmstadt, Germany
The partial substitution of Ag with Cu in the chalcopyrite-based absorber of thin film solar cells is a promising approach towards higher power conversion efficiencies. The resulting (Ag,Cu)(In,Ga)Se2 (ACIGSe) alloy achieves a bandgap widening up to 0.2 eV, increased grain growth and a lower melting temperature. The latter might reduce structural defects and therefore recombination losses in the absorber. This is favorable especially for wide-bandgap solar cells, used as top subcells in tandem devices, whose device performance is mainly limited by deep defects. To gain a better understanding of the diffusion on the (I) sublattice, we experimentally explored the interdiffusion of Cu(In,Ga)Se2 and Ag(In,Ga)Se2 layers by in-situ X-ray diffraction (IS-XRD) and glow discharge optical emission spectroscopy. Besides the positive aspects of Ag-alloying, thermodynamic simulations have shown a miscibility gap for temperatures between 100°C and 400°C. It is theoretically proposed, that ACIGSe with a high Ga content and with a [Ag]/([Ag]+[Cu]) ratio between 0.25 and 0.75 decomposes into Ag-rich and Ag-poor phases. We have studied the phase stability of Ga-free and Ga-rich samples using IS-XRD during post-annealing processes.