Tandem Solar Modules: More Power From The Twin Pack
Semiconductor combination of perovskite and CIGS promises increased efficiency in photovoltaics
The efficiency of commercially available solar modules can only be increased to a limited extent. Significantly more potential is offered by the use of two light-active layers in tandem solar modules. The promising technology could be the future. In the "Capitano" project, researchers combine thin-film solar modules based on perovskite semiconductors with semiconductors made of copper, indium, gallium and selenium (CIGS). The combination enables highly efficient tandem solar cells with an efficiency potential of over 30 percent with all the advantages of thin-film technology. Project partners are the Center for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) as coordinator, the Karlsruhe Institute of Technology (KIT) and the company NICE Solar Energy in Schwäbisch Hall.
Tandem solar modules consist of two different types of solar modules stacked on top of each other, which make better use of the spectrum of sunlight than the respective single solar cell. As a result, the multiple solar modules have a higher efficiency. Significantly more than 30 percent are theoretically possible - with simple silicon solar cells, for example, 29 percent is already over.
Couple is better
There are now several variants of tandem modules available. In CIGS perovskite development, a perovskite solar cell converts the light into electricity in the visible part of the solar spectrum. The underlying CIGS solar cell absorbs the light in the near-infrared spectrum, which penetrates the perovskite solar cell. Both solar cells use thin-film technologies that can be produced on square-meter substrates. This could significantly reduce costs while at the same time achieving high efficiency.
Higher efficiencies through collaboration
Professor Michael Powalla, Member of the Board and Head of Photovoltaics at ZSW and Professor at KIT, refers to the excellent composition of the consortium: "Due to the broad competence from the basics to mass production in the project, I expect great progress in the further development of this promising technology. " Ulrich W. Paetzold, junior research group leader at KIT adds: "We are developing the next generation of high-efficiency thin-film tandem solar modules with an efficiency above 30 percent. Promising fields of application are, for example, highly efficient solar modules for building-integrated photovoltaic solutions."
The project Capitano
The project started in July 2019 and runs for three years. The Federal Ministry for Economic Affairs and Energy is supporting it with a total of around 5.2 million euros, of which 2.1 million euros go to KIT. The aim of the project is to develop cells with stable higher efficiencies, which can be interconnected to form efficient tandem solar modules. The industrial partner NICE is to evaluate production on an industrial scale and to evaluate the costs.
The ZSW develops CIGS modules with adapted absorption spectrum (bandgap) and optimized surface and researches semitransparent perovskite solar cells and modules with high efficiency and transparency. The perovskite coating is to be tested with industry-relevant processes such as slot casting. Important sub-aspects here are optimized intermediate layers and adapted transparent contact layers. The results will be incorporated in the realization of series-connected tandem solar cells and modules. The environmental compatibility of the manufacturing process is also being evaluated.
In this project, KIT will develop new materials and processes as well as prototypes for the production of semitransparent perovskite solar cells and solar modules with an adapted absorption spectrum (band gap), high efficiency and high transparency. In particular, scalable production methods such as slot casting or deposition from the gas phase in vacuum are in the foreground. In view of the complex architecture of the tandem solar cells, the scientists are developing a lighting management concept for improved luminous efficacy. Yield calculations are also part of the task package.
The company NICE Solar Energy GmbH provides the other partners with CIGS small solar modules from its CIGS innovation line for the production of the tandem solar modules. The manufactured tandem solar modules then rated it in terms of their industrial scalability. A cost comparison with single-junction CIGS solar modules is also part of the agenda. An annual production capacity of 300 megawatts is assumed - this is a production quantity on an industrial scale.
About The ZSW
The Center for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) is one of the leading institutes for applied research in the fields of photovoltaics, regenerative fuels, battery technology and fuel cells as well as energy system analysis. The three ZSW locations Stuttgart, Ulm and Widderstall currently employ around 260 scientists, engineers and technicians. There are also 90 scientific and student assistants. The ZSW is a member of the Innovation Alliance Baden-Württemberg (innBW), an association of 13 non-university, business-related research institutes.
About NICE Solar Energy
NICE Solar Energy is a vertically integrated research and development joint venture with shareholders China Energy Group, Shanghai Electric Group Co., Future Science City and Manz AG. As the world's leading research joint venture, we are working to continuously increase the efficiency of CIGS solar modules and open many new fields of application for them. More than 160 employees at the Schwäbisch Hall site work on the implementation of an ambitious technology roadmap, the continuous increase in the efficiency of CIGS solar cells, and on ensuring the maximum investment security of the respective applications.
About KIT
As "The Research University in the Helmholtz Association", KIT creates and communicates knowledge for society and the environment. The aim is to make significant contributions to the global challenges in the fields of energy, mobility and information. Around 9,300 employees work together on a broad, disciplinary basis in natural sciences, engineering, business, humanities and social sciences. Its 25,100 students prepare the KIT for responsible tasks in society, economy and science through a research-oriented university degree program. The innovation activity at KIT bridges the gap between knowledge and application for social benefit, economic prosperity and preservation of our natural livelihoods. For more information, visit http://www.energie.kit.edu.
Source: The Karlsruhe Institute of Technology (KIT)