Printed solar panels could generate power from existing infrastructure

A multi-disciplinary research team at Swansea University has invented a novel solar panel printing process.
Ameya Paleja
The roll to roll printed solar cells at Swansea University
The roll to roll printed solar cells at Swansea University

Swansea University  

  • Printing solar panels could significantly improve the scale of deployment of solar panels.
  • With printed solar panels, even existing infrastructure could be turned into renewable energy generation centers.
  • The efficiency of the panels is currently low but they are made using non-toxic materials and production can be easily scaled.

With the world racing to switch to renewable sources of energy, investments in solar power are picking up speed. Although the technology has been commercially available for a few decades now, the pace of its adoption his often slowed by constraints such as cost or the lack of availability of land for large solar farms.

Perovskite-based cells are the newest addition to photovoltaics, and their arrival has helped researchers greatly improve the energy conversion of solar cells.

Researchers at the Sustainable Product Engineering Center for Innovative Functional Industrial Coatings (SPECIFIC), a UK Innovation and Knowledge Center at Swansea University, have taken perovskite-based solar cells a step further by making them compatible with the roll-to-roll fabrication process used in printed solar cell manufacturing.

This advance is expected to further reduce the cost of making perovskite-based solar panels, thereby improving their adoption.

Interesting Engineering spoke to David Beynon, Senior Research Officer at SPECIFIC. Beynon walked us through the conventional production process of perovskite-based solar cells and explained how this process could be replaced by something more conducive to roll-to-roll printing for large-scale production.

Printed solar panels could generate power from existing infrastructure
David Beynon, Senior Research Office at SPECIFIC

The interview has been edited slightly for clarity.

Interesting Engineering: Why are printable solar cells important — what advantages do they offer over regular solar cells?

David Beynon: There is a need for low-carbon renewable energy as we move away from fossil fuels and therefore the demand for solar power generation is growing. Silicon photovoltaics is an established technology with installation increasing globally, however, these solar panels are energy intensive to manufacture, rigid, and susceptible to damage, particularly during transport. 

There is potential for perovskite solar cells to enhance the efficiency of existing silicon PV through the manufacture of silicon-perovskite tandem cells, this is the focus of companies such as Oxford PV. Our research into roll-to-roll printing of flexible perovskite solar cells however has the advantage of high volume low cost manufacture on robust flexible plastic substrates that are easy to transport and deploy.

What is carbon electrode ink and how is it made? 

In perovskite solar cells, typically the semiconductor and photoactive perovskite layers are deposited and then an evaporated metal electrode is put down to complete the photovoltaic cell.

The electrode evaporation, typically a precious metal such as gold, takes place in a vacuum chamber where the metal is heated until it evaporates passing through a mask to condense on the sample. This is a wasteful, high-cost process that is not compatible with high-speed roll-to-roll printing. 

The carbon electrode ink replaces this process enabling roll-to-roll printing of the full perovskite device stack so that plastic film can be fed into the printing press and complete solar cells come out at the end.

The carbon ink is specifically formulated for compatibility with the perovskite material and the slot die coating process by combining conductive carbon particles, polymer binder, and solvent.

The combination of polymer and solvent is carefully controlled so that the ink can flow through the coating head to produce continuous electrodes which are formed when the solvent evaporates leaving the conductive carbon bound together by the polymer binder.

Printed solar panels could generate power from existing infrastructure
Dr David Beynon (Left) and Dr Ershad Parvazian (Right) hold a sample of the new fully roll-to-roll (R2R) coated product.

What is the rate of production that you have achieved in the lab? How does it compare to conventional production methods? 

We operate at pilot scale roll-to-roll production having standardized processing at a rate of 1m/min, although we have the capacity to increase throughput this gives the production of 18,000cm2 in 20min compared to the typical spin coating method where 156cm2 can be coated in the same time frame.

Even at this lab scale printing production rate is 115 times higher than conventional perovskite coating.

Energy conversion efficiencies using perovskite solar cells are pretty high these days. Has your method of production impacted efficiency? 

Our entire roll-to-roll coated cells have an efficiency of over 10%, a great achievement for this first demonstration of this technology but it does lag behind the record efficiencies now achieved for perovskite solar cells.

This discrepancy is partly due to the process, increased size of devices, and lack of selectiveness in sample selection however it is also partly due to our philosophy of working only with truly scalable systems.

Printed solar panels could generate power from existing infrastructure
The solar cells being printed at Swansea University's facility.

This limits the chemistries we can select as we only use lower toxicity solvents and our production is entirely in ambient air (with humidity control) as opposed to the highly controlled dry nitrogen glovebox environments employed for the highest efficiency cells.

Is your team working to improve the efficiencies of the solar cells?

Yes, with this first demonstration, we have a platform to use as a base for improved processing, chemistry, and interlayers. We are working to improve all layers of the device stack including replacing the perovskite material with the higher-performing multi-cation perovskite materials.

What sort of savings can be expected when producing solar cells using your method? 

It is difficult to simply quantify the savings as we are not yet seeing the economies of scale through purchasing at the volumes required for commercial production but we are in the process of a techno-economic evaluation. The production process however is analogous to the printing of packaging which is extremely low cost per square meter.

What new applications are now possible using your printable solar cells? 

The new applications are brought about by the volumes, flexibility, low weight, and therefore ease of installation. This allows surfaces that previously couldn’t accept solar cells to be used for power generation particularly in the built environment by design and by retrofit.

These flexible perovskite solar panels could be applied to curved surfaces, roofs, facades, and polytunnels, making use of existing structures for power generation and avoiding the complications of competing desires for land usage.

Printed solar panels could generate power from existing infrastructure
Printable flexible solar panels could help resolve concerns over land usage by solar power plants.

How do you plan to scale up the adoption of the technology?

We are exploring the licensing of our technology and have strategic industrial and academic partnerships for accelerating commercial adoption.

What was the experience working in a multi-disciplinary team like?

Working in a multi-disciplinary team is a pleasure and always more productive to work collaboratively with a team bringing a variety of skills and perspectives to link all strands together. 

Particularly in this project, it was critical to have experts in specialist analysis techniques such as X-ray photoelectron spectroscopy and photoluminescence bringing expert analysis and new methodologies for applying the analysis to understand what is happening at an atomic scale over a wide area. Then having identified critical factors bringing solutions from materials, formulation, and processing perspectives.

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