Schlüsselwörter
(Deutsch)
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Tandem-Solarzelle, Photovoltaik, Perowskit-Solarzellen
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Schlüsselwörter
(Englisch)
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Tandem solar cell, photovoltaics, perovskite solar cell
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Kurzbeschreibung
(Englisch)
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This project aims to realize photovoltaic (PV) energy harvesting systems based on tandem solar cells with efficiencies beyond those achievable with state-of-the-art industrial single-junction cells by combining the unique technological components – record cells absorbing various parts of the solar spectrum – recently realized by Swiss research institutes. By themselves, the new multi-junction cells will be highly complex systems, and will open opportunities for tomorrow’s electricity power plants and for consumer electronic applications, including e.g. watches and powering of low-consumption electronics. The project is supported by key players of the PV field (Meyer Burger) and of the watch and electronic industries (Swatch Group R&D and EM Marin).
Since decades, the PV market has been dominated by wafer-based crystalline silicon (c-Si) solar cells with lab record efficiencies of 25%, and production efficiencies of 17-22%. As these values are already close to the theoretical limit of single-junction c-Si cells, further improvements will not be possible by incremental technological innovation. One of the most promising approaches to overcome this limit is to combine two single-junction cells with different optical band gaps to form tandem solar cell systems. This concept has been successfully employed for concentrator PV systems using expensive III-V semiconductors and for thin film Si solar cells, such as a-Si/μc-Si tandem cells with limited efficiencies. Highly efficient tandem cell systems involving c-Si or copper indium gallium selenide (CIGS) bottom cells have so far not been successfully realized, mainly due to the difficulty to find a suitable wide-band gap top cell that delivers the necessary photocurrent while exhibiting excellent electrical properties.
Recently, the situation drastically changed with the emergence of highly efficient wide-band gap thin-film solar cells that deliver high photocurrents, based on perovskite absorbers. In addition, low-band gap cells based on CIGS compounds have recently reached efficiencies beyond 20%, thus are nearly as efficient as the best c-Si cells. In parallel, heterojunction c-Si solar cells with record efficiencies in the infra-red have been demonstrated. We believe that these recent developments from Swiss labs enable industrially relevant tandem systems with efficiencies beyond 30%.
The project consortium has vast experience and top-notch infrastructures required to fabricate state-of-the-art devices for all these high-efficiency PV technologies, and each group is world-leading in one or several of them. Each of these technologies will be adapted and optimized to be integrated into tandem cells. Specifically, PV-lab at EPFL will develop dedicated a-Si/c-Si heterojunction bottom cells, EMPA chalcogenide cells with tuneable band gaps such as CIGS cells, and LPI at EPFL perovskite-sensitized solar cells. Finally, the broad PV-related capabilities of the project consortium are leveraged for up-scaling and the development of PV energy harvesting demonstrator systems, an activity that will be led by CSEM.
This project involves a mix of technologies at various length scales to realize large area ultra-high performance photovoltaic energy harvesting systems with the potential to provide both the terawatts of sustainable energy needed for future generations as well as to enable a next generation of ubiquitous wearable and electronic applications with integrated power source.
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Publikationen / Ergebnisse
(Englisch)
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CH3NH3PbI3 perovskite / silicon tandem solar cells: characterization based optical simulations M. Filipic et al., Optics Express 23(7):A263-78 · April 2015
Raman Spectroscopy of Organic–Inorganic Halide Perovskites, M. Ledinský, Journal of Physical Chemistry Letters 6(3):401–406 · February 2015
Efficient Near-Infrared-Transparent Perovskite Solar Cells Enabling Direct Comparison of 4-Terminal and Monolithic Perovskite/Silicon Tandem Cells, J. Werner et al., ACS Energy Lett., 2016, 1 (2), pp 474–480.
Zinc tin oxide as high-temperature stable recombination layer for mesoscopic perovskite/silicon monolithic tandem solar cells, J. Werner, Applied Physics Letters 109, 233902 (2016)
Probing Photocurrent Nonuniformities in the Subcells of Monolithic Perovskite/Silicon Tandem Solar Cells, Z. Song et al., J. Phys. Chem. Lett. 2016, 7, 5114−5120
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Schlussbericht
(Deutsch)
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Viele etablierte Solarzellen-Technologien, darunter solche mit Absorber-Schichten aus kristallinem Silizium (Si) und Kupfer-Indium-Gallium-Diselenid (CIGS), erreichen Wirkungsgrade nahe ihrer Effizienzgrenze. Innovative Ansätze werden deshalb benötigt, um ihren Wirkungsgrad weiter erheblich zu steigern. Einer der vielversprechendsten Ansätze besteht darin, verschiedene PhotovoltaikTechnologien zu Tandem-Solarzellen zu kombinieren. Dieses Projekt hat gezeigt, dass die noch junge Perowskit-Technologie mit bereits etablierten Technologien zu hoch-effizienten Tandemzellen kombiniert werden kann. Dafür wurden Perowskit-Zellen mit hoher Infrarot-Transparenz entwickelt und entweder mit einer Si-Zelle oder einer CIGS-Zelle kombiniert. Für aufeinandergeschichtete Tandemzellen wurden so Wirkungsgrade von 25.6 % (Si) und 22.7% (CIGS) erreicht. Zusätzlich wurden Perowskit-Zellen direkt auf Si-Zellen abgeschieden, um monolithische Tandemzellen herzustellen. Diese erreichten Wirkungsgrade bis zu 22.7% dank einer Ladungsträger-Rekombinationsschicht aus nano-kristallinem Si, welche die optischen Verluste minimierte. Die etablierten PhotovoltaikTechnologien wurden für ihre Verwendung in Tandemzellen angepasst, indem ihre InfrarotSpektralantwort verbessert wurde. Für CIGS-Zellen geschah dies vor allem durch Anpassen der Absorber-Schicht, bei Si-Zellen indem Elektroden mit hoher Transparenz in diesem Wellenlängenbereich entwickelt wurden. Die Skalierbarkeit der noch jungen Perowskit-Technologie wurde anhand von Modulen mit einem Wirkungsgrad von 16% für eine Fläche von 14 cm2 gezeigt. Gegen Ende dieses Projekts wurde die Lebensdauer der Perowskit-Zellen erhöht, indem Verkapselungsverfahren und Perowskit-Materialien mit verbesserter Stabilität entwickelt wurden. Dieses Projekt war Teil eines gleichnamigen Nano-tera.ch Projekts mit Projekt-Nummer 530695, welches zusätzlich die Entwicklung von neuartigen Solarzellen mit Nanodrähten aus Galliumarsenid beinhaltete.
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Schlussbericht
(Englisch)
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Established photovoltaic (PV) technologies, such as crystalline silicon (c-Si) and copper indium gallium diselenide (CIGS) solar cells, are approaching their practical efficiency limit. For further substantial performance improvements, disruptive approaches are therefore required. A highly promising approach lies in combining PV technologies to form tandem solar cells. This project demonstrated that the emerging perovskite PV technology can be combined with established technologies to form highly efficient tandem devices. Specifically, perovskite solar cells with high near-infrared transparency were developed and mechanically stacked onto either c-Si or CIGS cells. This led to tandem cell efficiencies of up to 25.6% and 22.7%, respectively. In addition, perovskite cells were directly deposited onto c-Si bottom cells, resulting in monolithic tandem cells with efficiencies of up to 22.7%. These monolithic tandems were made using a nano-crystalline Si recombination junction, which reduced optical losses. The optimization of the photovoltaic technologies used as bottom cells focused on the improvement of their near-infrared spectral response. For CIGS cells, this was reached by tuning the absorber layer composition, for c-Si cells by using highly transparent contacts. Up-scaling of the perovskite technology was demonstrated by fully-laser-scribed modules with efficiencies of up to 16% for an active area of 14 cm2. In addition, a reliable encapsulation process for perovskite cells was developed. In the final phase of the project, major effort was dedicated to improve the stability of perovskite cells. By developing advanced perovskite materials, cells with strongly improved stability were obtained. This project was part of a Nano-tera.ch project with the same name (project number: 530695), which additionally included research on more prospective solar cell technologies, such as gallium arsenide nanowire cells.
Zugehörige Dokumente
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Schlussbericht
(Französisch)
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Les technologies actuelles de cellules photovoltaïques, telles que celles à base de silicium (Si) ou de cuivre, indium, gallium et diselenide (CIGS), approchent leur limite d’efficacité. Des approches innovantes sont ainsi nécessaires pour dépasser cette limite. Ce projet démontre que de nouvelles technologies peuvent être combinées avec celles établies pour former des cellules tandems à haute efficacité. Dans cette optique, des cellules à base d’une perovskite, un matériau transparent dans l’infrarouge, ont été développées. Celles-ci ont été empilées mécaniquement sur des cellules de Si ou CIGS afin d’atteindre des efficacités de 25.6% et 22.7%, respectivement. Ces cellules pérovskites ont aussi été déposées directement sur la face avant de cellules Si afin de former des tandems monolithiques, démontrant des efficacités de 22.7%. Ces tandems monolithiques utilisent une jonction de recombinaison à base de silicium nanocristallin, ce qui permet de réduire les pertes optiques. L’optimisation des cellules photovoltaïques placées à l’arrière d’une tandem s’est concentrée sur l’amélioration de leur réponse spectrale dans le proche infrarouge. Pour les cellules CIGS, ceci a été atteint en modifiant la composition du matériau absorbeur, tandis que les contacts ont été rendu plus transparents pour les cellules Si. La fabrication de modules gravés par laser d’une efficacité de 16% pour une dimension de 14 cm2 a démontré qu’il était possible de transposer à plus grande échelle la technologie des cellules perovskite. De plus, une méthode d’encapsulation robuste a été mise au point. La phase finale du projet s’est concentrée sur l’augmentation de la stabilité des cellules pérovskites, ce qui a été rendu possible en modifiant la composition de la perovskite. Ce projet a fait partie d’un projet Nano-tera.ch du même nom (numéro 530695). Celui-ci s’est aussi penché sur d’autres technologies solaires telles que celles à base de nanofils d’arséniure de gallium.
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