EU funding strengthens solar cell research at HZB
Ultra-high vacuum system in the Energy Materials In-Situ Lab (EMIL) that will combine industry-relevant deposition tools with a suite of complementary advanced characterization methods. © R.G. Wilks
Marcus Bär and his team are participating in two international projects being funded under the EU Horizon 2020 research programme. Both research projects are concerned with development and optimisation of high-efficiency thin-film solar cells based on chalcopyrites (“Sharc 25") and kesterites (“SWInG”). These two projects will together bring in about 900,000 EUR of additional research funding for solar cell research.
The two projects, Sharc25 and SWInG, will be funded under the EU’s Low-Carbon Energy section. “The advanced material characterisation at HZB will focus on the interface characteristics of solar cell structures. Particularly, the complementarity of the suite of instruments at the newly established EMIL lab at BESSY II will benefit this research”, explains Prof. Marcus Bär, who heads the Young Investigator Group - Interface Design at HZB.
“Sharc25" stands for “Super High-Efficiency Cu(In,Ga)Se2 Thin-Film Solar Cells Approaching 25%”. The project will focus on pushing the performance of Cu(In,Ga)Se2 (CIGSe) thin-film solar cells towards 25 % conversion efficiency, which is considerably higher than the efficiency of market-dominating polycrystalline silicon cells. Achieving this level of efficiency would provide a significant competitive advantage for the European thin film PV industry. The research project will be coordinated by the Centre for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) and involves research partners from seven European countries. The project funding is 6.15 million EUR in total, of which 450,000 EUR is allocated to HZB. “We will be systematically investigating the layer stacks, particularly focusing on understanding the properties and processes at the interfaces. Optimising the interface behaviour is a fundamental prerequisite for driving the efficiency towards its theoretical limit”, says Bär.
SWInG (Development of Thin-Film Solar Cells based on Wide Band-Gap Kesterite Absorbers) is to receive 3.8 million EUR and will be coordinated by imec (Interuniversity Micro-Electronics Centre/Belgium) and includes partners from the Netherlands, France, Germany, and Sweden. 450,000 EUR are allocated to HZB. The objective of the research is to develop inexpensive, dependable tandem solar cells that have the potential of converting more than 30% of sunlight into electricity. The wide band-gap solar cell absorbers necessary for this will be achieved by modifying the composition of the kesterite. “Kesterite absorber layers are desirable, because they consist of Earth-abundant elements. In addition, the band gap can be adjusted by varying the composition of the material, matching it to the requirements of the tandem solar cell”, explains Bär.
- 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.
- Perovskite solar cells: Predictions of long-term stabilityReliable statements about the long-term stability of perovskite solar cells are still difficult to make. However, a new study by Dr Carolin Ulbrich’s team, published in the renowned journal Joule, highlights which methods are useful for this purpose and identifies areas where further research is needed.