PhD - Genk | More than two weeks ago
Tandem solar cells are the next generation photovoltaics technology exceeding the Shockley Queisser limit of single junction solar cells. In tandem devices, the absorption of the broad solar spectrum is split into the high band gap top cell and low band gap bottom cell, thus thermalization losses related to high energy photons are minimized. With the rapid development of perovskite (PSK) materials, including PSK absorbers with high band gap (> 1.6 eV), tandem solar cell research based of PSK technology has garnered plenty of interest. When a PSK based top cell is combined with a Si bottom cell, tandem cells are being developed using cheap and highly efficient photovoltaic materials.
These PSK based tandem cells are mostly explored in two different configurations. The first is a 4-terminal (4T) approach in which the top and bottom cells are electrically separated and hence 4 wires are required to connect a photovoltaic module to the system. The second option is 2-terminal (2T) tandem architecture. In this architecture the top and bottom cells are connected in series by a recombination junction and only the front and rear contacts are accessed. This configuration is preferred from an industrial application point of view as a module based on this solar cell architecture only requires 2 wires to connect to the system. However, due to the current matching condition of a 2T configuration, the device operation is very sensitive to the band gap selection of the top and bottom absorber and for spectral variations of outdoor illumination.
Instead of series connection of individual top and bottom sub-cells as in a monolithic 2T tandem module, a parallel connection of the strings of top and bottom cells (sub-modules) at module level will be investigated. In this scheme, only 2T are produced at module level. In case of parallel connection, the electric current of both strings is summed up, since the illumination power and thus the electrical photocurrent is divided between the top and bottom cells. One of the main advantages of the proposed concept is that the parallel connection of top cell and bottom cell strings does not require current matching of cells, thus it is expected to be much less dependent on spectral variations in realistic outdoor conditions. Thus, higher energy yield during realistic PV module operation is expected.
Si mini modules and PSK top modules will be fabricated, interconnected and tested. The PSK mini-modules used on top of Si mini-modules will consist of parallel connected sub-minimodules. Appropriate encapsulant materials and lamination process conditions compatible with the sensitive PSK cell stack and the thermal budget requirements will be selected and developed. The top and bottom modules will then be further connected into one 2T-V module by overlapping the bussing ribbons of the two sub-modules. The physical interconnection can be accomplished using electric conductive adhesive or soldering. Finished modules will be tested upon their stable output under various spectral conditions.
The Ph.D. candidate will join imec’s PV technology group performing world-class research on advanced thin-film and wafer-based technologies at our state-of-the-art research facilities located at the Energyville Campus in Genk. The student will work in both the thin film (PSK top cell) as well the waferPV (Si bottom cell) team and has the potential to collaborate with industrial partners.
Required background: Electrical engineering, industrial engineering, physics
Type of work: 10% literature, 70% experimental, 20% modelling
Supervisor: Bart Vermang
Daily advisor: Jessica de Wild
The reference code for this position is 2023-075. Mention this reference code on your application form.