Dresden 2026 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 45: Perovskite and Photovoltaics: Spectroscopy
HL 45.1: Talk
Thursday, March 12, 2026, 15:00–15:15, POT/0006
The influence of air and light exposure on alkali-metal doped Cu(In,Ga)Se2 absorber materials measured with in-situ TRPL and XPS — •P. Stötzner, S. Sobisch, A. Stauffenberg, H. Kempa, R. Scheer, and S. Förster — Martin-Luther-Universität Halle-Wittenberg, Germany
Copper indium gallium diselenide (Cu(In,Ga)Se2/CIGSe) is a promising thin-film solar cell absorber. Alkali-metal doping, especially in combination with heavy alkali metals, enhances solar cell efficiencies. However, air and light exposure (ALE) of the absorber reduces the solar cell efficiency. This is a result of the diffusion of sodium and oxygen toward the absorber surface, which is accompanied by a degradation of the charge-carrier lifetime of doped CIGSe absorbers [1,2].
Here, we study the ALE effect for CIGSe doped with K and cominations of Na and K as well as Na and Rb. Our studies combine X-ray photoelectron spectroscopy (XPS) and in-situ time-resolved photoluminescence (TRPL) conducted in one ultrahigh vacuum system, addressing changes in the chemical composition and charge-carrier lifetime. The setup is completed by a high-pressure gas cell enabling for controlled exposure to specific environments.
We find that the charge-carrier lifetime of non-doped absorbers is unaffected by ALE and all alkali-metal doped absorbers degrade due to ALE. XPS shows that the most heaviest alkali metal present and oxygen are accumulated at the surface. While this effect is reversable over time, the degradation of the charge-carrier lifetime is permanent.
[1] DOI: 10.1063/1.4992116 [2] DOI: 10.1002/pip.3041
Keywords: CIGSe; alkali doping; TRPL; XPS