Complex thin films are a key enabler of a range of multiple multibillion Euro energy technologies - including energy efficient materials, energy generation and power electronics. Such different technologies share common metrology challenges related to quality, performance and reliability. More information at https://www.hymet.ptb.eu/
One of the major problems, which is currently limiting the state-of-the-art photovoltaic solar cells, is related to the material degradation under sun light. We study the possibility that the root cause for the degradation is related to the interaction of light with copper ions. Our approach could lead to a rather simple solution in avoiding power loss: implementing charge on the surface to attract the copper ions.
Black silicon absorbs light very efficienctly over a wide spectral range. The challenge of this material has been related to the surface passivation due to the increased surface area of the nanostructures. Our research is focused on the passivation of the black silicon by atomic layer deposition that allows very conformal coating.
Defects and impurities (e.g. oxygen, metals, dislocations, point defects) are most often harmful when present in semiconductor devices. With deep understanding of relevant defect reactions and gettering mechanisms, it is possible to tolerate the defects without affecting the device performance. Our studies include gettering e.g. by P/B diffusion, SiOx precipitates, Al layer, implantation. The applications can be either high purity silicon or solar grade / upgraded metallurgical silicon. Our research activities include also the development of characterization methods for defects, e.g. based on minority carrier lifetime.
Atomic layer deposition (ALD) technology has roots in Finland. In close collaboration with Beneq Oy, we study the fundamental passivation mechanisms of ALD thin films as well as develop the processes and equipment both in n-type and p-type cells.
Copper contacts have already taken place in microelectronics. Because of the cheaper price as compared to currently used silver, copper will most likely appear soon in commercial solar cells. Our silicon solar cell processing line includes copper metallization by sputtering or evaporation followed by electroplating. We study among other things the suitability of interconnecting ribbon to the copper contacts.
The group uses extensive clean room facitilites at Micronova Nanofabrication Centre for material research and device fabrication.
Understanding the multilevel phenomena that enables inorganic atomic layer deposition to provide barrier coatings for highly-porous 3-D printed plastic in vacuums
Excellent Responsivity and Low Dark Current Obtained with Metal-Assisted Chemical Etched Si Photodiode
Efficient surface passivation of germanium nanostructures with 1% reflectance
Black ultra-thin crystalline silicon wafers reach the 4n2 absorption limit – application to IBC solar cells
Spatial uniformity of black silicon induced junction photodiode responsivity
Surface passivation of Germanium with ALD Al2O3: Impact of Composition and Crystallinity of GeOx Interlayer
Is Carrier Mobility a Limiting Factor for Charge Transfer in Tio2/Si Devices? A Study by Transient Reflectance Spectroscopy
Chemical Excitation of Silicon Photoconductors by Metal-Assisted Chemical Etching
Comparison of SiNx-based Surface Passivation Between Germanium and Silicon
Plasma-enhanced atomic layer deposited SiO2 enables positive thin film charge and surface recombination velocity of 1.3 cm/s on germanium
Associate Professor Hele Savin
Email: hele.savin at aalto.fi
Tel.: +358 50 5410 156
Department of Electronics and Nanoengineering
Aalto University School of Electrical Engineering
P.O. Box 13500, 00076 Aalto, Finland
Micronova, 4th floor, room 4156
Tietotie 3, 02150 Espoo