“Workhorse” of silicon photovoltaics combined with perovskite in tandem for the first time

A standard silicon solar cell is combined with a perovskite top cell. This tandem solar cell could reach high efficiencies.

A standard silicon solar cell is combined with a perovskite top cell. This tandem solar cell could reach high efficiencies. © Silvia Mariotti / HZB

Cross-sectional schematics of the perovskite−POLO−PERC tandem solar cell.

Cross-sectional schematics of the perovskite−POLO−PERC tandem solar cell. © HZB

In the HySPRINT laboratory at HZB, the perovskite experts are constantly working on new improvements.

In the HySPRINT laboratory at HZB, the perovskite experts are constantly working on new improvements. © Michael Setzpfand/HZB

So-called PERC cells are used in mass production of silicon solar cells, they are considered the workhorses of photovoltaics, dominating the market. Now two teams from HZB and the Institute for Solar Energy Research in Hamelin (ISFH) have shown that such standard silicon cells are also suitable as a basis for tandem cells with perovskite top cells. Currently, the efficiency of the tandem cell is still below that of optimised PERC cells alone, but could be increased to up to 29.5% through targeted optimisation. The research was funded by the German Federal Ministry of Economics as part of a joint project.

Tandem cells made of silicon and perovskite are able to convert the broad energy spectrum of sunlight into electrical energy more efficiently than the respective single cells. Now, for the first time, two teams from HZB and ISFH Hameln have succeeded in combining a perovskite top cell with a so-called PERC/POLO silicon cell to form a tandem device. This is an important achievement, since PERC silicon cells on p-type silicon are the "workhorse" of photovoltaics, with a market share of about 50% of all solar cells produced worldwide. They are largely optimised, long-term stable and temperature stable. Therefore, it is particularly interesting for the commercialisation of a perovskite-silicon tandem technology to develop a "perovskite tandem upgrade" for PERC cells. The cooperation took place within the framework of the joint project P3T, which is funded by the Federal Ministry of Economics and coordinated by HZB.

The team at ISFH used an industry-compatible PERC process for the backside contact of the silicon bottom cells. On the front side of the wafer, another industrialisable technology was used, the so-called POLO contact, which was adapted here for the small-area proof of concept cells.

Perovskite expertise at HZB

The following process steps took place at HZB: A tin-doped indium oxide recombination layer was applied as a contact between the two subcells. On top of this, a perovskite cell was processed with a layer sequence similar to that in the current world record tandem cell on n-type silicon heterojunction cells, made by HZB. The first perovskite PERC/POLO tandem cells produced in this way achieve an efficiency of 21.3% on an active cell area of about 1 cm². This efficiency is thus still below the efficiency of optimised PERC cells in this feasibility study. "However, initial experimental results and optical simulations indicate that we can significantly improve the performance through process and layer optimisation," explains Dr. Lars Korte, the corresponding author of the study.

PCE estimated at 29,5 %

The experts estimate the Power Conversion Efficiency (PCE) of these perovskite/silicon tandem solar cells with PERC-like sub-cell technology at 29.5 %. The next steps for further efficiency increases are already clear: Dr. Silvia Mariotti from the HZB team had identified the coverage of the silicon surface by the perovskite as potential for improvement: "For this purpose, one could adapt the surface of the silicon wafers and thus quickly increase the efficiency to about 25%," says Mariotti. This is then already significantly higher than the efficiency of PERC single cells.

arö


You might also be interested in

  • Best Innovator Award 2023 for Artem Musiienko
    News
    22.03.2024
    Best Innovator Award 2023 for Artem Musiienko
    Dr. Artem Musiienko has been awarded a special prize for his groundbreaking new method for characterising semiconductors. At the recent annual conference of the Marie Curie Alumni Association (MCAA) in Milan, Italy, he received the MCAA Award for the best innovation. Since 2023, Musiienko has been carrying out his research project with a postdoctoral fellowship from the Marie Sklodowska Curie Actions in Antonio Abate's department, Novel Materials and Interfaces for Photovoltaic Solar Cells (SE-AMIP).
  • Neutron experiment at BER II reveals new spin phase in quantum materials
    Science Highlight
    18.03.2024
    Neutron experiment at BER II reveals new spin phase in quantum materials
    New states of order can arise in quantum magnetic materials under magnetic fields. An international team has now gained new insights into these special states of matter through experiments at the Berlin neutron source BER II and its High-Field Magnet. BER II served science until the end of 2019 and has since been shut down. Results from data at BER II are still being published.

  • Where quantum computers can score
    Science Highlight
    15.03.2024
    Where quantum computers can score
    The travelling salesman problem is considered a prime example of a combinatorial optimisation problem. Now a Berlin team led by theoretical physicist Prof. Dr. Jens Eisert of Freie Universität Berlin and HZB has shown that a certain class of such problems can actually be solved better and much faster with quantum computers than with conventional methods.