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A mature Quokka for everyone – advancing the capabilities and accessibility of numerical solar cell simulations

Periodic Reporting for period 1 - Quokka Maturation (A mature Quokka for everyone – advancing the capabilities and accessibility of numerical solar cell simulations)

Reporting period: 2016-02-01 to 2018-01-31

A key task in tackling several of the world’s most pressing problems, comprising climate change, energy security and environmental pollution, consists in the fast replacement of the world’s largely fossil-based and non-sustainable energy system by renewable energies. Extraordinary political and technological advances in the last decade have made photovoltaics (PV) cost-competitive with mainstream electricity generation, which is now a key to transforming the energy system towards sustainability.
This project helps accelerating the R&D efforts into solar cells by addressing a lack of sophisticated but accessible simulation software. It based on the free and popular solar cell simulation tool “Quokka”, originally developed by the Marie-Curie fellow. Supported by hosting the action at one of the world’s leading PV research institutes, Fraunhofer Institute for Solar Energy Systems (ISE), Quokka was successfully re-coded and substantially enhanced towards a powerful commercial version called “Quokka3”. It is closing the gap between the two alternatives available to date: on the one hand powerful commercial software from the semiconductor industry, being complex, expensive and not dedicated to solar cells; on the other hand a plethora of free / inexpensive tools developed by the PV community, all with limited scope and substantial simplifications. Quokka3’s dedication to cover most of the relevant solar cell physics (but not more) makes it easy-to-use, yet powerful, with even some unprecedented capabilities like modelling a full-size silicon solar cell in 3D.
With the release of Quokka3 during the project, PV researchers world-wide are now able to support their solar cell R&D efforts by a moderately priced yet very powerful simulation tool. Indeed the “Quokka community” has grown significantly from a few tenths of highly specialized users to more than hundred active users worldwide, making Quokka the most used simulation software for silicon photovoltaics. By the end of the project, it was already able to support many R&D activities at Fraunhofer ISE by the involvement of the fellow in current research projects, as evidenced by many scientific publications. In the final phase of this project, a German business has been founded to market Quokka3, which attracted already several customers at the time of writing the report. This step was already planned in the proposal of Quokka Maturation and thus emphasizes the success and impact of this project.
The work performed in the project can roughly be categorized into i) software development, ii) application to scientific projects at Fraunhofer ISE and partners, iii) business formation and Quokka3 marketing.
The software development and the application to other projects at Fraunhofer ISE were strongly interwoven, benefiting both sides: the involvement into other scientific projects helped to identify relevant physics and desired simulation capabilities, and thus effectively guided the choice of what kind of numerical models to implement into the software. The scientific projects did then benefit of early access to those newly developed capabilities, often significantly being superior to the state-of-the-art, as well as excellent control over those features by the software developer being involved, e.g. for troubleshooting. In turn, the intensive usage of such new features did provide an excellent testing environment, both for validation the implemented models as well as for bug-finding and -fixing. The project thus achieved a true win-win situation, as evidenced by the ongoing commitment of both sides to continue the relationship.
Two major examples of the software enhancement supporting scientific projects results are: i) the capability for full-cell 3D modelling, enabling to thoroughly investigate edge effects of lab-scale record cells, half-cells, and shingle solar cells; ii) thoroughly model coupled electronic-ionic carrier transport, which is a decisive step towards understanding the many non-ideal characteristics observed in the novel perovskite solar cells.
Next to 15 scientific publications in peer-reviewed journals and conferences, as well as 5 workshops within Europe, the main public dissemination of the results takes place by the commercialization of Quokka3 ( and the continued hosting of the free predecessor Quokka2. The fellow has started a business in Germany, with several licenses agreements already signed, and many more potential customers having expressed interest. Furthermore, an IP agreement with Fraunhofer ISE was established, which enables him to be part-time employed besides the Quokka3 business, and thus to continue the highly valued win-win collaboration for both sides.
The state-of-the-art for solar cell simulations before the start of the project did consist in two extremes. On the one hand there are few powerful commercial simulation software from the integrated-circuit semiconductor field. Those tools are very powerful with respect to being able to describe semiconductor physics in high detail and generality. However, modelling solar cells does require only a subset of those physical models. This renders the application of such software for solar cells an “overkill” in many cases, meaning a long learning curve for using the software, high license costs and high computational requirements. For solar cells, non-detrimental simplifications can be employed to the relevant subset of the physical models, leading to the much simpler user-interface and (in many cases) much better computational efficiency of Quokka3 compared to the existing commercial semiconductor software. On the other hand, there is a plethora of free / inexpensive tools available for solar cell modeling. Each tool is dedicated to handle only a subset of the models relevant for solar cells, often employing simplifications detrimental for many desired use cases, and often being limited in numerical performance. Quokka3 improves this situation by addressing (most of) the relevant physical models within a single tool with state-of-the-art numerical performance, with a specific focus on silicon solar cells.
Quokka3 thus can simulate solar cells at an unprecedented combination of ease-of-use, completeness, accuracy and speed, closing the gap between the “overkill” of semiconductor software and the plethora of free but limited tools. This is evidenced by the great interest of the PV community in Quokka3, both to use it for scientific projects, as well as for licensing. The project successfully triggered the public release of Quokka3 as a medium-priced commercial software and resulted in an ongoing close collaboration with Fraunhofer ISE. It is thus expected to substantially impact world-wide solar cell R&D, by providing the researchers with a capable simulation software specifically for their needs.