Rear surface passivation of ultra-thin CIGS solar cells using atomic layer deposited HfOx
Institute for Material Research (IMO), Hasselt University (partner in Solliance), Wetenschapspark 1, Diepenbeek 3590, Belgium
2 IMEC division IMOMEC (partner in Solliance), Wetenschapspark 1, Diepenbeek 3590, Belgium
3 EnergyVille, Thorpark, Poort Genk 8310 & 8320, Genk 3600, Belgium
4 IMEC (partner in Solliance), Kapeldreef 75, Leuven 3001, Belgium
5 KTH-Royal Institute of Technology, Stockholm 11428, Sweden
6 Université Catholique de Louvain-UCLouvain, Louvain-la-Neuve 1348, Belgium
7 Department of Electrical Engineering, KU Leuven, Kasteelpark Arenberg 10, Heverlee 3001, Belgium
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Received in final form: 8 October 2020
Accepted: 18 November 2020
Published online: 8 December 2020
In this work, hafnium oxide layer is investigated as rear surface passivation layer for ultra-thin (550 nm) CIGS solar cells. Point contact openings in the passivation layer are realized by spin-coating potassium fluoride prior to absorber layer growth. Contacts are formed during absorber layer growth and visualized with scanning electron microscopy (SEM). To assess the passivating qualities, HfOx was applied in a metal-insulator-semiconductor (MIS) structure, and it demonstrates a low interface trap density in combination with a negative density of charges. Since we used ultra-thin devices that are ideal to probe improvements at the rear, solar cell results indicated improvements in all cell parameters by the addition of 2 nm thick HfOx passivation layer with contact openings.
Key words: Solar cells / ultra-thin films / copper indium gallium selenide / surface passivation layer / hafnium oxide
© G. Birant et al., published by EDP Sciences, 2020
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.