Keeping up the passion
Tabitha Amollo (in red top) with her research group of students and technical staff. © private
Dr. Tabitha A. Amollo is a researcher and lecturer at Egerton University in Njoro in Kenya. She holds a Ph.D. in physics from the University of KwaZulu-Natal, South Africa. Her research interests focus on developing cutting-edge nanomaterials for energy conversion devices including graphene nanomaterials. She published a number of articles in reputable journals. At Egerton University, she is the head of a young team to explore dye-sensitive solar cells, she is a chairperson of the Physics Department, and she coordinates the undergraduate program and gives lectures to undergraduates and postgraduate physics students.
Here in Germany, there are not many women in physics. How is it in Kenya?
That’s similar, only few girls choose physics. In my case, in high school, I had a good physics teacher. I was the best student and he gave me a science book as an award. And this really encouraged me to take physics in the following grade.
What are you working on in your lab?
I am totally fascinated by new organic materials, such as dye sensitive materials for solar cells of the next generations. We are developing such new materials, combining them with graphene and nanostructures, and examining their photovoltaic performance.
What is your connection to BESSY II?
Last November, Dr. Antje Vollmer gave a great talk at my university, Egerton, and we all got really excited about the options at BESSY II. We are really looking forward to start experiments. I will come for the user meeting and beamtime in June 2023 and I will bring some of my students along. It will be a very busy week, we plan to measure our samples to inquire their quantum efficiencies, but also to examine them under the Transmission Electron Microscope, Scanning Electron Microscope and with Atomic Force Microscopy. And I hope to get into contact with the PV-experts at HZB, they have great expertise in perovskite materials, another very fascinating class of materials.
Do you have a vision for the future?
I want to contribute to society with my research in solar energy. We just had a black out here in the lab, we often do, it is a problem. So I am really working to improve the energy system. Solar energy has great potential to provide cheap electricity, and it is fossil free, so it will not contribute to global heating.
How did you start your own lab? What were the first steps?
Well, a research lab requires equipment, and for phyisics experiments, these are expensive. I won two research grants, in 2020 and 2022, which financed the equipment acquisition. The focus of my research lab is the development of innovative solar energy conversion materials and technologies.
What is your advice to young students?
I would advise them to keep up their passion, their curiosity. There always are obstacles, and passion gives you the energy to surmount them.
This blogpost is part of a series on our cooperation with scientists from Kenya.
- 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.