HZB Newsroom

Inorganic perovskite solar cells made of CsPbI₃ are stable over the long term and achieve good efficiencies. A team led by Prof. Antonio Abate has now analysed surfaces and interfaces of CsPbI₃ films, produced under different conditions, at BESSY II. The results show that annealing in ambient air does not have an adverse effect on the optoelectronic properties of the semiconductor film, but actually results in fewer defects. This could further simplify the mass production of inorganic perovskite solar cells.

An HZB physicist has developed a new method for the comprehensive characterisation of semiconductors in a single measurement. The "Constant Light-Induced Magneto-Transport (CLIMAT)" is based on the Hall effect and allows to record 14 different parameters of transport properties of negative and positive charge carriers. The method was tested now on twelve different semiconductor materials and will save valuable time in assessing new materials for optoelectronic applications such as solar cells.

The world's best tandem solar cells, consisting of a silicon bottom cell and a perovskite top cell, can today convert around one-third of incident solar radiation into electrical energy. These are record values, especially for a potentially very low-cost technology. A team at HZB is now providing the scientific data for the first time and describing how this development was achieved in the renowned journal Science. 

Solar cells made from metal halide perovskites achieve high efficiencies and their production from liquid inks requires only a small amount of energy. A team led by Prof. Dr. Eva Unger at Helmholtz-Zentrum Berlin is investigating the production process. At the X-ray source BESSY II, the group has analyzed the optimal composition of precursor inks for the production of high-quality FAPbI₃ perovskite thin films by slot-die coating. The solar cells produced with these inks were tested under real life conditions in the field for a year and scaled up to mini-module size.

Dr. Artem Musiienko has earned a prestigious Maria Skłodowska Curie Postdoctoral Fellowship for his research project HyPerGreen. In the group of Prof. Antonio Abate, HZB, Musiienko will explore and improve lead-free perovskite solar cells with the goal to increase their efficiency to more than 20 %.  

Perovskite semiconductors promise highly efficient and low-cost solar cells. However, the semi-organic material is very sensitive to temperature differences, which can quickly lead to fatigue damage in normal outdoor use. Adding a dipolar polymer compound to the precursor perovskite solution helps to counteract this. This has now been shown in a study published in the journal Science by an international team led by Antonio Abate, HZB. The solar cells produced in this way achieve efficiencies of well above 24 %, which hardly drop under rapid temperature fluctuations between -60 and +80 Celsius over one hundred cycles. That corresponds to about one year of outdoor use.

The current world record of tandem solar cells consisting of a silicon bottom cell and a perovskite top cell is once again at HZB. The new tandem solar cell converts 32.5 % of the incident solar radiation into electrical energy. The certifying institute European Solar Test Installation (ESTI) in Italy measured the tandem cell and officially confirmed this value which is also included in the NREL chart of solar cell technologies, maintained by the National Renewable Energy Lab, USA.

In order to transfer tandem solar cells from laboratory scale to production, HZB is cooperating with the solar module manufacturer Meyer Burger, which has great expertise in heterojunction technology (HJT) for silicon modules. Within the framework of this cooperation, mass production-ready silicon bottom cells based on heterojunction technology are to be combined with a top cell based on perovskite technology.

Tandem solar cells, which combine two different perovskite semiconductors, promise high efficiencies and can be produced with very little energy input. Such modules could even be bendable. Together with partners from industry and research, HZB expert Prof. Steve Albrecht is working to realise this vision. His team recently succeeded in producing an all-perovskite tandem solar cell with a certified efficiency of 27.2 %. A conversation about the opportunities and challenges of the perovskite-perovskite technology.

By the end of 2021, teams at HZB had presented perovskite silicon tandem solar cells with an efficiency close to 30 percent. This value was a world record for eight months, a long time for this hotly contested field of research. In the renowned journal Nature Nanotechnology, the scientists describe how they achieved this record value with nanooptical structuring and reflective coatings.

On Friday, 17 June, a delegation from Singapore visited HZB. Heng Swee Keat, Deputy Prime Minister of Singapore, was accompanied by the Ambassador to Singapore in Germany, Laurence Bay, as well as representatives from research and industry.

King Carl XVI Gustaf of Sweden as well as a group of business leaders from large corporations such as Ericsson, Nordholt, Vattenfall, ABB, Schneider Electric and Swedish representatives from the public sector and academia visited the Adlershof Technology Park on 11 May 2022.

Climate change has Amran Al-Ashouri concerned. As a physicist, he knows how urgently and quickly measures need to be taken to limit the global temperature increase to between 1.5 and 2 degrees Celsius. In his private life, the 29-year-old scientist is accordingly a member of the association “climactivity”, which aims to educate as many people as possible about important matters in climate protection.

Q CELLS and Helmholtz-Zentrum Berlin achieve a new world record efficiency for a 2-terminal tandem solar cell combining a mass-production ready silicon bottom cell based on Q.ANTUM technology and a top-cell based on perovskite technology. The efficiency is 28.7%.

So-called PERC cells are used in mass production of silicon solar cells, they are considered the workhorses of photovoltaics, dominating the market. Now two teams from HZB and the Institute for Solar Energy Research in Hamelin (ISFH) have shown that such standard silicon cells are also suitable as a basis for tandem cells with perovskite top cells. Currently, the efficiency of the tandem cell is still below that of optimised PERC cells alone, but could be increased to up to 29.5% through targeted optimisation. The research was funded by the German Federal Ministry of Economics as part of a joint project.

On February 17, 2022, the Adlershof Dissertation Prize was awarded for the 20th time. Dr. Amran Al-Ashouri (3rd from right) from the HZB young investigator research group "Perovskite tandem solar cells" received the prize endowed with 3,000 euros. The physicist is researching how new organic contact layers can be used to optimize highly efficient perovskite silicon tandem solar cells.

Eva Unger was now appointed as W2 professor at Humboldt-Universität zu Berlin. Prof. Dr. Eva Unger leads a research group at HZB. She develops scalable technologies for the production of perovskite semiconductors for low-cost and highly efficient solar cells.

Researchers from Innovation Lab HySPRINT at Helmholtz-Zentrum Berlin (HZB) and Humboldt Universität zu Berlin (HU) have used an advanced inkjet printing technique to produce a large range of photodetector devices based on a hybrid perovskite semiconductor. By mixing of only three inks, the researchers were able to precisely tune the semiconductor properties during the printing process. Inkjet printing is already an established fabrication method in industry, allowing fast and cheap solution processing. Extending the inkjet capabilities from large area coating towards combinatorial material synthesis opens the door for new possibilities for the fabrication of different kind of electronic components in a single printing step.

An international team of experts has collected data on metal halide perovskite solar cells from more than 15,000 publications and developed a database with visualisation options and analysis tools. The database is open source and provides an overview of the rapidly growing knowledge as well as the open questions in this exciting class of materials. The study was initiated by HZB scientist Dr. Eva Unger and implemented and coordinated by her postdoc Jesper Jacobsson.

Three HZB teams led by Prof. Christiane Becker, Prof. Bernd Stannowski and Prof. Steve Albrecht have jointly managed to increase the efficiency of perovskite silicon tandem solar cells fabricated completely at HZB to a new record value of 29.80 %. The value has now been officially certified and is documented in the NREL-charts. This brings the 30 percent mark within reach.

Dr. Antonio Abate investigates perovskite semiconductors for low-cost and highly efficient solar cells and heads a large research group at the Helmholtz Centre Berlin. Now he has accepted a W2 professorship in the Department of Chemistry at Bielefeld University.

An international team at HZB and Charles University Prague has investigated how charge carriers in so called MAPI-perovskite semiconductors interact with different defects. They show that a large proportion of defects quickly releases trapped charge carriers. These results could help to further improve the properties of perovskite solar cells.

At first glance, it looks like an ordinary wristwatch. But its glass taps the energy of the sun. A research group at Helmholtz-Zentrum Berlin has made this possible. Their transparent photovoltaics have now even made it into mass production, securing the team this year's HZB Technology Transfer Award.

Metal-organic perovskite materials promise low-cost and high-performance solar cells. Now a group at HZB managed to de-couple the different effects of self-assembled monolayers of organic molecules (SAMs) that reduce losses at the interfaces. Their results help to optimise such functional interlayers.

Tin halide perovskites are currently considered the best alternative to their lead-containing counterparts, which are, however, still significantly less efficient and stable. Now, a team led by Prof. Antonio Abate from HZB has analysed the chemical processes in the perovskite precursor solution and the fluoride compounds in detail. Using a clever combination of measurement methods at BESSY II and with NMR at the Humboldt-University Berlin, they were able to show that fluoride prevents the oxidation of tin and leads to a more homogeneous film formation with fewer defects, increasing the quality of the semiconductor layer.

The HZB is coordinating a major European collaborative project to open up new opportunities for the European solar industry. The VIPERLAB project involves 15 renowned research institutions from Europe, as well as Switzerland and Great Britain. It will be funded within the framework of the EU's Horizon 2020 programme for the next three and a half years with a total of 5.5 million euros, from which the HZB will receive just under 840,000 euros. 

Using small-angle scattering at the PTB X-ray beamline of BESSY II, an HZB team was able to experimentally investigate the colloidal chemistry of perovskite precursor solutions used for solar cell production. The results contribute to the targeted and systematic optimization of the manufacturing process and quality of these exciting semiconductor materials.

A long-cherished dream of materials researchers is a solar cell that converts sunlight into electrical energy as efficiently as silicon, but that can be easily and inexpensively fabricated from abundant materials. Scientists at the Helmholtz-Zentrum Berlin have now come a step closer to achieving this. They have improved a process for vertically depositing a solution made from an inexpensive perovskite solute onto a moving substrate below. Not only have they discovered the crucial role played by one of the solvents used, but they have also taken a closer look at the aging and storage properties of the solution.

An HZB team has published a report in the journal Science on the development of its current world record of 29.15% efficiency for a tandem solar cell made of perovskite and silicon. The tandem cell provided stable performance for 300 hours – even without encapsulation. To accomplish this, the group headed by Prof. Steve Albrecht investigated physical processes at the interfaces to improve the transport of the charge carriers.

For the production of high-quality metal-halide perovskite thin-films for large area photovoltaic modules often optimized inks are used which contain a mixture of solvents. An HZB team at BESSY II has now analysed the crystallisation processes within such mixtures. A model has also been developed to assess the kinetics of the crystallisation processes for different solvent mixtures. The results are of high importance for the further development of perovskite inks for industrial-scale deposition processes of these semiconductors.

Scientists at HZB have printed and explored different compositions of caesium based halide perovskites (CsPb(Br_xI_1−x)₃ (0 ≤ x ≤ 1)). In a temperature range between room temperature and 300 Celsius, they observe structural phase transitions influencing the electronic properties. The study provides a quick and easy method to assess new compositions of perovskite materials in order to identify candidates for applications in thin film solar cells and optoelectronic devices.

Perovskites are regarded as promising materials for solar cells, able to be manufactured at low cost while at the same time being extremely efficient. They are particularly suitable for tandem solar cells that combine a cell made of silicon and one of perovskite. As a result, sunlight is more completely used when generating electrical energy. So far, the advantages of such cells have only been available for use at small laboratory scale. With two new, highly innovative production facilities, researchers at the Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) are now creating the basis for future production on an industrial scale.

The region of the spectrum that can be utilised for producing electrical energy can be considerably extended by converting low-energy (longer wavelength) photons into high-energy (shorter wavelength) photons. But so far, this has only been possible at high intensities of light. Now for the first time, scientists from the Helmholtz-Zentrum Berlin (HZB) and the Federal Institute for Materials Research and Testing (BAM) have been able to produce a usable effect from relatively weak light by combining certain nanoparticles with what is known as a meta-surface. This paves the way for future applications in photovoltaics, for the detection of biological substances, and for electrical-field sensors.

In order to develop efficient opto-electronic devices such as solar cells or LEDs, it is crucial to improve the quality of the semiconductors. To achieve this, it is necessary to determine the luminescence yield of the semiconductor material. For this characterization, a research team at HZB has developed a new measuring device that precisely determines the luminescence and is also very compact. In order to evaluate the potential for commercial applications, the team now receives a Field Study Fellowship from the Helmholtz Association.

A team of researchers from the Helmholtz-Zentrum Berlin (HZB) and Humboldt-Universität zu Berlin has succeeded for the first time in producing light-emitting diodes (LEDs) from a hybrid perovskite semiconductor material using inkjet printing.This opens the door to broad application of these materials in manufacturing many different kinds of electronic components.The scientists achieved the breakthrough with the help of a trick: "inoculating" (or seeding) the surface with specific crystals.

The promising halide perovskite materials for solar energy conversion show high efficiencies, but this comes at a cost: The best perovskite materials incorporate toxic lead which poses a hazard to the environment. To replace lead by less toxic elements is not easy since lead-free perovskites show lower stability and poor efficiencies. Now, an international collaboration has engineered a new hybrid perovskite material with promising efficiency and stability.

Steve Albrecht is researching on perovskite solar cells and holds several efficiency world records with his team. Back in his schooldays, he was going to become either a competitive gymnast or a scientist. He chose science, but the same athletic ambition still drives his research forward.

A special branch in the famous NREL-chart for solar cell world records refers to a newly developed tandem solar cell by HZB teams. The world-record cell combines the semiconductors perovskite and CIGS to a monolithic "two-terminal" tandem cell. Due to the thin-film technologies used, such tandem cells survive much longer in space and can even be produced on flexible films. The new tandem cell achieves a certified efficiency of 24.16 percent.

On 11 February 2020, Max Grischek received the Erhard Höpfner Thesis Prize, worth 2000 euros, which is awarded by a jury of the Berlin Scientific Society for outstanding theses. Grischek studied at the Technische Universität Berlin and wrote his master thesis in the young investigator research group "Perovskite Tandem Solar Cells" at HZB.

Experts from 51 research institutions have now agreed on the procedures for measuring the stability of perovskite solar cells and assessing their quality. The consensus statement was published in Nature Energy and is considered a milestone for the further development of this new type of solar cell on its way to industrial application.

In the race for ever higher efficiency levels, an HZB development team has once again pulled ahead. The groups of Steve Albrecht and Bernd Stannowski have developed a tandem solar cell made of the semiconductors perovskite and silicon, that converts 29.15 per cent of the incident light into electrical energy. This value has been officially certified by the CalLab of the Fraunhofer Institute for Solar Energy Systems (ISE) and means that surpassing the 30 per cent efficiency mark is now within reach.

On November 7, 2019, Michael Müller, Governing Mayor of Berlin and Senator for Science and Research, honoured outstanding research achievements for the twelfth time. Prof. Dr. Steve Albrecht was honoured this year with the "Nachwuchspreis" (Young Talent Award) for his research on novel tandem solar cells. Albrecht teaches as a junior professor at the Institute for High Frequency and Semiconductor System Technologies at the Technical University of Berlin and heads the research group "Perovskite Tandem Cells" at the Helmholtz-Zentrum Berlin. The Young Talent Award is given to scientists who are not older than 35 years and is endowed with 10,000 euros.

On 15 November, the best innovation project from the HZB will be awarded the Technology Transfer Prize 2019. The award ceremony is open to the public and will take place at 2 p.m. in the BESSY II auditorium at the HZB location in Berlin-Adlershof. All projects submitted to the competition will be presented in an exhibition starting Monday, October 21, initially in Wannsee, and starting November 4 in Adlershof.

A HZB team has successfully raised funds from the “Helmholtz European Partnering Program” of the Helmholtz Association to expand cooperation with partners of the University of Ljubljana, Slovenia. The topics of the cooperation are tandem solar cells made of perovskite and silicon and, in particular, their precise characterisation.

A team headed by Prof. Steve Albrecht from the HZB will present a new world-record tandem solar cell at EU PVSEC, the world's largest international photovoltaic and solar energy conference and exhibition, in Marseille, France on September 11, 2019. This tandem solar cell combines the semiconducting materials perovskite and CIGS and achieves a certified efficiency of 23.26 per cent. One reason for this success lies in the cell’s intermediate layer of organic molecules: they self-organise to cover even rough semiconductor surfaces. Two patents have been filed for these layers.

Christiane Becker uses microscopic structures to increase the amount of light captured in solar cells and is currently scaling up the technology for industrial application. “On top of everything else, there’s this spirit at HZB that we are working on the renewable energies of the future, and that is incredibly inspiring,” she relates in portrait.

This year's Karl Scheel Prize from the Physikalische Gesellschaft zu Berlin honours Steve Albrecht of the Helmholtz-Zentrum Berlin für Materialien und Energie for his work in the field of highly efficient tandem solar cell absorbers made of metal-halide perovskites.

More than 200 people have chosen their favourite pictures in the photo competition "Moments at the HZB" during the Long Night of Science. The winners have now been chosen, but the decision was extremely close.