The neglected influence of zinc oxide light-soaking on stability measurements of inverted organic solar cells |
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Authors: | Marcella Günther Soroush Lotfi Sergio Sánchez Rivas Dominic Blätte Jan P Hofmann Thomas Bein Tayebeh Ameri |
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Affiliation: | 1. Department of Chemistry and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität (LMU), Butenandtstr. 5-13, 81377 Munich, Germany;2. Surface Science Laboratory, Department of Materials and Earth Sciences, Technical University of Darmstadt, Otto-Berndt-Strasse 3, 64287 Darmstadt, Germany |
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Abstract: | Although zinc oxide (ZnO) is one of the most commonly used materials for electron transport layers in organic solar cells (OSCs), it also comes with disadvantages such as the so-called light-soaking issues, i.e., its need for exposure to UV light to reach its full potential in OSCs. Here, the impact of ZnO light-soaking issues on stability measurements of OSCs is investigated. It is found that in the absence of UV light a reversible degradation occurs, which is independent of the used active layer material and accelerates at higher temperatures but can be undone with a short UV exposure. This reversible aging is attributed to the re-adsorption of oxygen, which for manufacturing reasons is trapped at the interface of ZnO, even in an oxygen-free environment. This oxygen can be removed with a UV pretreatment of the ZnO but at the expense of device efficiency and production that has to take place in an oxygen-free environment. This study establishes that stability measurements of ZnO-containing OSCs must be performed exclusively with a light source including a UV part since the usage of a simple white light source – as often reported in the literature – can lead to erroneous results. |
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Keywords: | light-soaking organic solar cells stability zinc oxide |
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