Fully Solution-Processed, Light-Weight, and Ultraflexible Organic Solar Cells
Ezgi Nur Güler a b, Andreas Distler a b, Andreas Bornschlegl a, Larry Lüer a, Robin Basu a, Christoph J. Brabec a b c, Hans-Joachim Egelhaaf a b c
a Friedrich-Alexander-Universität Erlangen-Nürnberg, Faculty of Engineering, Department of Material Science, Materials for Electronics and Energy Technology (i-MEET), Martensstraße 7, 91058 Erlangen, Germany
b Solar Factory of the Future (SFF), Friedrich-Alexander-Universität Erlangen-Nürnberg, Energie Campus Nürnberg (EnCN), Fürther Straße 250, 90429 Nürnberg, Germany
c Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (HI ERN), Forschungszentrum Jülich GmbH (FZJ), Immerwahrstraße 2, 91058 Erlangen, Germany
Proceedings of New Generation Photovoltaics for Space (PVSPACE)
Online, Spain, 2022 June 21st - 22nd
Organizers: Narges Yaghoobi Nia, Aldo Di Carlo, Luigi Schirone and Mahmoud Zendehdel
Contributed talk, Larry Lüer, presentation 004
DOI: https://doi.org/10.29363/nanoge.pvspace.2022.004
Publication date: 8th June 2022

Organic photovoltaic (OPV) devices have the potential to be superior to other PV technologies in space applications because they can play out two of their main advantages, namely their high flexibility and low weight, maximizing the specific power which is the central figure of merit. With ultrathin active layers of submicron thickness, the heaviest part in OPV technology is the substrate. In outer space, mechanical loading is minimal (no gravitation, wind gusts, or snow loads), so that a further decisive reduction of weight could be achieved by building solar cells without substrates, relying only on the mechanical support of the thin barrier layers that are used for encapsulation.  However, this poses challenges on the reliable multilayer deposition process, as well as on the resilience against folding/unfolding during transport, which must be solved in a cost-effective way that is amenable to mass production.

In this work, we present fully solution-processed (which includes both electrodes) semitransparent organic solar cells (OSCs) without substrates, with performance comparable with conventional indium tin oxide-based devices. Direct cell fabrication onto barrier films leads to the elimination of the additional polyethylene terephthalate substrate and one of the two adhesive layers in the final stack of an encapsulated OPV device by replacing the industrial state-of-the-art sandwich encapsulation with a top-only encapsulation process. This yields significantly thinner and lighter ‘product-relevant’ PV devices. In addition to the increase of the specific power to 0.38 W g−1, which is more than four times higher than sandwich-encapsulated devices, these novel OSCs exhibit better flexibility and survive 5000 bending cycles with 4.5 mm bending radius. Moreover, the devices show comparable stability as conventionally encapsulated devices under constant illumination (1 sun) in ambient air for 1000 h. Finally, degradation under damp heat conditions (65 ◦C, 85% rh) was investigated and found to be determined by a combination of different factors, namely (UV) light soaking, intrinsic barrier properties, and potential damaging of the barriers during (laser) processing. [1]

In the outlook, we discuss how the barrier layers, and the photoactive layer can be stabilized against hard radiation using high throughput experimentation driven by physics-informed artificial intelligence.

The authors thank Mitsubishi Chemical for providing research samples of barrier foils. The authors also acknowledge the ‘Solar Factory of the Future’ as part of the Energy Campus Nuremberg (EnCN), which is supported by the Bavarian State Government (FKZ 20.2-3410.5-4-5). The authors also acknowledge funding from the Federal Ministry for Economic Affairs and Climate Action (Project ‘OPV4IoT’, FKZ 16KN098724) and from the European Union’s Horizon 2020 research and innovation program under Grant Agreement No. 952911 (‘BOOSTER’). Fruitful discussions within the framework of the European Union’s Horizon 2020 research and innovation program under Grant Agreement No. 101007084 (‘CITYSOLAR’) are acknowledged. Support from the Deutsche Forschungsgemeinschaft (DFG; projects BR 4031/21-1 and BR 4031/22-1) is also acknowledged.

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