Electron Physics

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.