A realistic approach to increase the efficiency of photovoltaic (PV) devices above the Shockley-Queisser single-junction limit is the construction of tandem devices. This PhD focuses on the development of very high efficiency thin-film perovskite on chalcogenide (CuIn(Ga)Se2 = CI(G)S) tandem devices; where a more ideal band gap combination (i.e. 1.6-1.7 eV top solar cell + 1.0 eV bottom solar cell) can be applied as compared to perovskite on silicon (Si, with band gap = 1.1 eV) and perovskite on perovskite (partly or completely replacing Pb with Sn forming Pb-Sn perovskite, with band gap of ≥ 1.2 eV) tandem structures. See the Figure below.
Tandem solar cells are commonly fabricated in two distinct configurations: 2-terminal (2T) or 4-terminal (4T). The standard 2T or monolithic configuration requires the top and bottom cells to be connected in series, which requires current matching of both cells for optimum operation. Hence, their overall energy yield is substantially affected under non-standard spectral conditions. The 4T configuration circumvents this issue of current matching by electrically isolating the top and bottom cells. This configuration allows for independent optimization of the cells as well as modular fabrication. However, this configuration requires more than one transparent electrode that could result in additional parasitic absorption.
- Development of near-infrared (NIR)-optimized CI(G)S solar cells, which will be verified in 4T tandem devices. Efforts will be focused on bulk improvements (e.g., in terms of doping or band alignment at the pn-junction, and thickness reduction), surface passivation techniques (e.g. oxides with point contacts or Ga grading), and absorption enhancement (e.g., increasing rear internal reflectivity).
- Optimization of these NIR CI(G)S solar cells for integration into 2T tandem devices. Efforts will be focused on CI(G)S surface morphology improvements and interconnecting layer development (this way it becomes a substrate for perovskite solar cell growth), and assessment of recombination or tunnel junctions between the two sub-cells (e.g. concerning compatibility of these interlayers with adjacent materials).
The candidate will be a member of imec's thin film PV group, which consists of chalcogenide and perovskite research teams. The candidate will belong to the chalcogenide team but will cooperate a lot with the perovskite team.
Required background: Engineering Science
Type of work: 70% experimental, 10% modelling, 20% literature
Supervisor: Bart Vermang
Daily advisor: Marc Meuris
The reference code for this position is 2020-072. Mention this reference code on your application form.
Chinese nationals who wish to apply for the CSC scholarship, should use the following code when applying for this topic: CSC2020-34.