Printing solar panels can enhance deployment scale, converting existing infrastructure into renewable energy centers, despite current low efficiency, thanks to non-toxic materials and scalable production.
With the worldwide race to switch to renewable sources of energy, investment in solar energy is picking up pace.
Although the technology has been commercially available for a few decades now, its adoption has often been slowed by barriers such as cost or lack of land availability for large solar farms.
Perovskite-based cells are the newest development in photovoltaics, and their advent 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 a roll-to-roll fabrication process. In manufacturing printed solar cells.
The development is expected to further reduce the cost of manufacturing perovskite-based solar panels, thus improving their availability.
Intriguing Engineering spoke to SPECIFIC’s Senior Research Officer, David Bevan. Beynon walks us through the traditional production process for perovskite-based solar cells and how the process can be replaced with something more conducive to roll-to-roll printing for mass production.
Interview has been edited slightly for clarity.
Why Printable Solar Cells Matter – What Advantages Do They Offer Over Regular Solar Cells?
David Beynon: Low carbon renewable energy is needed as we move away from fossil fuels and therefore the demand for solar energy generation is increasing.
Silicon photovoltaics is an established technology with increasing global installation, however, these solar panels are energy-intensive to manufacture, rigid and susceptible to damage, especially during transportation.
The potential to increase the efficiency of existing silicon PV through the production of silicon perovskite tandem cells for perovskite solar cells is the focus of companies such as Oxford PV.
Our research on roll-to-roll printing of flexible perovskite solar cells has the advantage of low-cost manufacturing in large volumes on strong flexible plastic substrates that are easy to transport and deploy.
What Is Carbon Electrode Ink and How Is It Made?
In perovskite solar cells, semiconductor and photoactive perovskite layers are usually deposited and then an evaporated metal electrode is deposited on the bottom to complete the photovoltaic cell.
The electrode vaporizes, typically a precious metal such as gold, in a vacuum chamber where the metal is heated until it vaporizes as it passes through a mask to condense on the sample. This is a wasteful, high-cost process incompatible with high-speed roll-to-roll printing.
Carbon electrode ink replaces this process, enabling roll-to-roll printing of a complete perovskite device stack so that the plastic film can be fed into the printing press and finally the complete solar cells.
Carbon inks are specially formulated by combining carbon particles, polymer binders, and solvents compatible with perovskite materials and a slot die coating process.
The combination of polymer and solvent is carefully controlled so that the ink flows through the coating head to produce continuous electrodes that are formed when the solvent evaporates and binds the conductive carbon together with a polymer binder.
What is the yield rate you have achieved in the lab? How does it compare to conventional production methods?
We operate pilot-scale roll-to-roll production with standard processing at a rate of 1m/min, although we have the capacity to increase the throughput to 18,000cm2 in 20 minutes compared to typical spin coating. By the method of where 156cm2 can be coated in the same time frame.
Even this lab-scale printing has a production rate 115 times higher than conventional perovskite coatings.
Energy conversion efficiency using perovskite solar cells is quite high these days.
Has your production method affected efficiency?
The efficiency of our entire roll-to-roll coated cells is greater than 10%, which is a great achievement for this first demonstration of this technology, but it falls short of the record efficiency achieved for perovskite solar cells.
This disparity is partly due to the lack of choice in processes, increasing device size, and sample selection, but also partly to our philosophy of working only with truly scalable systems.
This limits the chemistries we can choose because we only use less toxic solvents and our production takes place entirely in ambient air (with humidity control) used for the highest performance cells. In contrast to the highly controlled dry nitrogen glove box environment.
Is your team working to improve the efficiency of solar cells?
Yes, with this first demonstration, we have a platform to use as a foundation for improved processing, chemistry, and interlayers. We are working to optimize all layers of the device stack, including replacing the perovskite material with a high-performance multication perovskite material.
What savings can be expected when producing solar cells using your method?
Savings are difficult to quantify simply because we are not yet looking at economies of scale by purchasing at the volumes required for commercial production, but we are in the process of a techno-economic evaluation. However, the production process is similar to packaging printing, which is extremely low cost per square meter.
Now what new applications are possible using your printable solar cells?
New applications have been brought about by volume, flexibility, light weight, and therefore ease of installation.
This allows surfaces that previously could not accept solar cells to be used to generate electricity, particularly in the built environment through design and retrofit.
These flexible perovskite solar panels can be applied to curved surfaces, roofs, facades, and polytunnels, utilizing existing structures for power generation and avoiding the complications of competing land use desires.
How do you plan for technology adoption at scale?
We seek to license our technology and have strategic industry and academic partnerships to accelerate commercial adoption.
What was the experience of working in a multidisciplinary team like?
Working in a multidisciplinary team is a joy and it is always more productive to work collaboratively with a team that brings a variety of skills and perspectives to connect all the strands.
In this project in particular, it was critical to have experts in analytical techniques such as X-ray photoelectron spectroscopy and photoluminescence to apply the analysis to understand what is happening on an atomic scale over a large area. And bring new procedures. It then identified the critical factors influencing the solution from a material, formulation, and processing standpoint.