Regensburg 2019 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 45: Photovoltaics (joint session HL/CPP)

CPP 45.2: Talk

Wednesday, April 3, 2019, 15:15–15:30, H36

Angle-resolved electroreflectance spectroscopy on CIGS solar cell absorber and buffer layers — •Jasmin Seeger¹, Jonas Grutke¹, Wolfram Witte², Dimitrios Hariskos², Oliver Kiowski², Heinz Kalt¹, and Michael Hetterich^1,3 — ¹Institute of Applied Physics, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany — ²Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW), 70563 Stuttgart, Germany — ³Light Technology Institute, KIT, 76131 Karlsruhe, Germany

Thin-film Cu(In,Ga)Se₂ (CIGS) solar cells can be further improved by replacing the standard CdS buffer layer with an alternative material, which leads to less absorption losses and therefore higher efficiencies. We employ electroreflectance spectroscopy (ER) for the destruction-free determination of the bandgap energies of different buffer materials grown by chemical bath deposition and to get insights into potential interdiffusion processes at the buffer/absorber interface. In this contribution, a new ER technique called angle-resolved electroreflectance spectroscopy (ARER) is presented, which allows the determination of the buffer’s bandgap energy. This is possible despite interference effects occurring due to the layered structure and despite the low signal due to the small buffer thickness. To demonstrate the applicability of ARER, results for absorber and CdS buffer layers are shown and compared to results from other ER measurement methods. Additionally, ARER is applied to solar cells with Zn(O,S) buffer layers, enabling the determination of the sulfur to oxygen ratio of the Zn(O,S) buffer and yielding hints for the possible formation of mixed phases.