Perovskite solar cells

A few years ago, perovskite solar cells were shown to be just as efficient as traditional crystalline silicon (c-Si) cells. There are therefore high expectations for this thin-film PV technology. And all indications are that these perovskite solar cells form a good tandem with c-Si solar panels. This tandem combination is expected to deliver cost-effective solar panels with yields of above 30%. In theory, tandems could achieve a maximum energy yield in excess of 40%.

Benefits of perovskite

There are important benefits in using perovskite as a semiconductor in PV modules:

• The raw materials used to produce perovskite are very cheap.
• Only a very thin layer of perovskite is needed in a solar cell. This reduces material costs even further.
• You can apply perovskite using a relatively simple deposition process (applying layers to a specific base – the substrate) that doesn’t require any costly machinery.
• You can deposit the layers of perovskite at low temperatures. This also keeps down production costs.
• It takes relatively little energy to make a perovskite cell. This means that the solar cell quickly recoups the costs of the energy that was needed to make it.

Perovskite solar cells on glass and foil

With the current state of perovskite solar cell technology, we can in principle achieve the same module efficiency on glass or foil as with another technology. In the Solliance partnership, we’ve already demonstrated a module efficiency of 16% with scalable production processes. The aim is to demonstrate 18 to 20% module efficiency by 2023. This and the low cost of the manufacturing process could make the perovskite solar cell a paradigm in the world of solar cells.

As with Copper Indium Gallium Selenide (CIGS), you can apply perovskite to glass, but also to flexible foils. In turn, you can integrate these into products, such as car roofs or siding. In the case of a transparent substrate such as glass or plastic, it’s also possible to make perovskite-based solar cells semi-transparent, for use in windows, for examples. 
 
Transparency is also needed for the promising application of perovskite solar cells in tandem technology. When they’re combined with silicon solar cells, the efficiency could exceed 30%.

Our perovskite research

In the Solliance partnership, led by TNO, Eindhoven University of Technology (TU/e) and imec, we have the technology and equipment in-house to develop and demonstrate the upscaling processes for perovskite PV modules. Both sheet-to-sheet and roll-to-roll. Considerable research and development are still needed for this project.

Efficiency

An important element of the research is improved efficiency. We’re working to create PV modules with the highest possible energy yield. To achieve this, we need to understand which factors affect the yield and how these can be influenced.

Stability

Stability is also important, as solar cells and the modules in use must be stable. This means that after 20 years, the output of the module when in use must not drop by more than 20% in relative terms. The factors that can have a negative impact on stability are water, air, temperature, electrical influence of the PV system, sometimes even light, and nearly always a complicated combination of these factors. For this reason, we’re constantly searching for the causes of possible instability. We try to remove these causes by using other materials and other processes.

Special protective layer

A disadvantage of perovskite is that it is not very water resistant. This places high demands on the barrier layer – the protective layer of PV modules. We’ve had good results with Atomic Layer Deposition (ALD). If we apply this technology for the inner layers, we don’t need such a strong barrier layer to make the modules moisture-resistant. In 2020, we showed that perovskite passes stress tests that we also use to test commercial modules.

Reduction of toxicity

The current generation of perovskite PV modules contain a very small amount of lead: approximately half a gram per square metre. Because lead may enter the environment if a solar panel is damaged, we’re investigating how great this harmful influence is and how we can limit it. Together with other Solliance partners, we’re identifying the potential risks and researching alternatives, with the aim of avoiding the use of lead.