Optical innovations for solar modules - which are the most promising?
Symbolic picture with Microsoft Copilot.
In 2023, photovoltaic systems generated more than 5% of the world’s electrical energy and the installed capacity doubles every two to three years. Optical technologies can further increase the efficiency of solar modules and open up new applications, such as coloured solar modules for facades. Now, 27 experts provide a comprehensive overview of the state of research and assess the most promising innovations. The report, which is also of interest to stakeholders in funding and science management, was coordinated by HZB scientists Prof. Christiane Becker and Dr. Klaus Jäger.
Photovoltaics (PV) has become one of the most cost-effective technologies for generating electricity. In November 2024, the world’s photovoltaic systems reached an installed capacity of two terawatts, and the growth rates and cost reductions are still enormous.
Expertise from 22 research institutions
‘At a recent workshop, we discussed how the optics community can contribute to the further growth of photovoltaics,’ says Prof. Christiane Becker, head of the Solar Energy Optics Department at HZB. Christiane Becker and her colleague Dr. Klaus Jäger then invited international experts to compile a comprehensive overview of PV technologies and optical innovations. In total, 27 renowned experts from 22 research institutions in 9 countries contributed to the review.
Most promising concepts
The article begins with an overview of the current state of photovoltaics on a terawatt scale. From this, the experts identify issues and topics, where the optics community can contribute to enable large-scale deployment. ‘We have also identified a number of optical concepts that are currently only on the threshold of economic viability, but which hold the most promise for advancing PV technology,’ says Christiane Becker. These include optical innovations in the field of multi-junction solar cells, which have the highest efficiencies and therefore have great potential to further reduce the levelized cost of electricity.
Ecological aspects
Improved manufacturing processes using an eco-design approach and minimising the consumption of critical raw materials are also discussed. Another chapter is devoted to coloured solar modules as building integrated PV solutions. ‘Especially in cities, we need to use facades and other surfaces too for solar energy conversion, and of course, it does matter how the PV modules look. Such innovative solar modules allow sophisticated aesthetic solutions,’ says Becker.
Christiane Becker and Klaus Jäger are convinced that this comprehensive review does not only help the scientific community, but also decision makers in research funding.
- Magnetic imaging: Micro-flowers increase the local magnetic fieldMaterials with magnetic nanostructures have many potential applications such as in spintronics. To explore such materials, nanoscale magnetic-sensitive imaging techniques are very useful, but up to now only weak magnetic fields could be applied during the imaging process. Now an international collaboration led by Dr. Sergio Valencia, HZB, has developed an approach that overcomes this limitation. The team designed tiny magnetic flux concentrators (MFCs), into which the sample is placed. The geometry of the MFCs resembles a flower with a number of petals which focus the applied magnetic field into its center. This greatly expands the magnetic field range available during imaging, and so the range of magnetic systems that can be investigated. The micro-flowers, enhancing magnetic fields locally, can find application in different nanometric magnetic microscopy techniques.
- CIGS-perovskite tandem cell achieves record efficiency of 25.5 %A Berlin-based team from HZB and Center for the Science of Materials Berlin (CSMB) at the Humboldt-Universität zu Berlin has set a new record for a tandem solar cell. Using a combination of a CIGS semiconductor layer and perovskite, along with several optimised intermediate layers, they were able to convert 25.5% of sunlight into electrical energy. The previous record for this combination of materials and this size of cell stood at 24.6%. The new record has been certified and is visible in the prestigious Solar Cell Efficiency Tables (the "Green Tables"), which serve as the definitive ledger for the global photovoltaic community.
- Disorder creates new properties in compound semiconductorsAn international research team has demonstrated that the intrinsic disorder of the compound semiconductor CuInSnS₄ can be exploited to influence its optical properties. While the atomic vibrations also sense the local disorder, their response is averaged over many different local environments and therefore appear isotropic, as expected for a cubic crystal. In contrast, the optical excitations, known as excitons, are much more sensitive to the local arrangement of atoms. Surprisingly, they show a direction-dependent optical response even though the average crystal structure is cubic. These findings shed new light on the relationship between disorder and material properties, opening up new options for targeted 'disorder engineering' in optoelectronic and photocatalytic devices.