Perovskites are a relative newcomer to the world of photovoltaics. Their ability to efficiently capture solar energy has made perovskites a technology well worth examining, and research on perovskite solar cells is going on worldwide.

However, what if the power absorbing benefits of perovskites could be put to use in applications other than solar cells? For example, retailers have been looking for ways to power up electronic shelf labels (ESL). If a store could use electronic shelf labels to show pricing, they could change the prices at the push of a button.

The problem is generating power. Having wires connecting to a battery is costly and not appealing to the eye. Could power be generated by a miniature solar cell operating indoors, in artificial light?

Saule Technologies believes that the answer is through perovskites. Headquartered in Poland, Saule Technologies has introduced the world’s first electronic shelf labels based on perovskite photovoltaic cells, or PESLs.

Perovskite photovoltaic cells from Saule Technologies display high efficiency also in artificial light. Unlike silicon solar cells, they are thin, light-weight and flexible. This could open the door for a one-hour long sale, for example. As the operation process is simple, price changes can be introduced centrally and synchronously across all retail stores within the chain.

“With PESLs, retail chains will be able to quickly reduce the prices of food products that are nearing their ‘best before’ dates. This will prevent huge amounts of food from being wasted, which in a world where so many people still go hungry appears unaffordable. The new trading tools provided by PESLs will let us save millions of tons of food each year,” said Olga Malinkiewicz, CTO of Saule Technologies, in announcing the new ESLs.

“We noticed a great opportunity in the large number of devices needed for this application, as well as the inherent limitation in features and battery life in the commercially established solutions,” added Olaf Szewczyk, acting communications director for Saule Technologies. “The market for electronic shelf labels is huge and is still rapidly growing. We offer more cost-effective, environment friendly and useful solutions.”

Szewczyk added that commercialization is coming very soon.

History of Saule Technologies

Saule Technologies’ beginnings can be traced to 2013. Malinkiewicz, then a PhD student at the University of Valencia in Spain, developed a unique method of producing solar cells based on perovskites on flexible foils, at low temperatures. For this achievement she was granted with the Photonics21 Student Innovation award in a competition organized by the European Commission.

Her discovery garnered international media attention. Soon after, Saule Technologies was established (2014), with one goal – to develop green, cost-competitive and versatile solar energy harvesting technology.

The company was founded by Malinkiewicz and two entrepreneurs, Piotr Krych and Artur Kupczunas, who realized that her breakthrough has the potential to impact the world on a massive scale. In 2015, Hideo Sawada, a Japanese entrepreneur and investor, represented by Huis Ten Bosch Co. Ltd., invested in Saule Technologies.

In 2021, Saule Technologies opened its first perovskite solar cells production line in Wroclaw, Poland, becoming the first company in the world to have commercial production of the perovskite photovoltaic technology. 

Saule Technologies has come very far in its R&D. Szewczyk said that perovskite photovoltaic cells are already almost as effective as traditional silicon photovoltaic cells, and there is still room for improvements.

“The theoretical maximum efficiency of silicon cells is 29.8%,” Szewczyk noted. “Perovskite photovoltaic cells can be theoretically even more efficient, circa 31%. What is even more important is that these devices – contrary to silicon cells – are very effective in harvesting artificial light, which makes them perfectly suitable for integration in indoor environments, i.e. IoT applications.”

Szewczyk said that the perovskite cells developed by Saule Technologies are able to work with 25.5% efficiency in operating conditions for IoT applications. The measurements were carried out at the Fraunhofer ISE group of Dr. Uli Würfel under 1000 lux illumination by a cold white LED, which represents the real-life environment for the first commercial application of these devices.

Szewczyk said that the unique features of Saule’s technology opens many new business opportunities.

“Flexible perovskite photovoltaic devices produced by Saule Technologies are very well suited for powering electronic devices in the indoor, low-light intensity conditions, making it a perfect solution for various Internet of Things (IoT) applications,” said Szewczyk. “They are also well-suited to serve as energy sources for BIPV, BAPV, e-mobility and many other business sectors. For example, Skanska is pioneering a method of covering office building exteriors with semi-transparent perovskite solar cells, provided by Saule Technologies, on a commercial scale.”

“Since perovskite solar cells are thin, light, and flexible, and we can use it almost everywhere,” Szewczyk concluded.” On roofs (also on irregular tiles), facades, windows (since it can be semitransparent – even on glass), clothes, laptops, smartphones, cars, you name it. It is the future of photovoltaics. We are very happy and proud Saule Technologies is the first company in the world commercializing this technology.”

Perovskite Electronic Shelf Labels

Electronic shelf labels are an interesting market for solar cells. Electronic labels with their own practically inexhaustible power source, not requiring the costly and time-consuming battery replacement, are not only cheaper and more convenient to use than the traditional ESLs, but also offer energy efficiency and enable resigning from batteries that are very harmful to the environment. Szewczyk noted that this is an important step in the implementation of the sustainable development strategy.

“Using perovskite photovoltaic cells, PESLs (Perovskite Electronic Shelf Labels) are a breakthrough solution also in view of their unique capabilities to communicate with customers of retail stores,” Szewczyk obsrved. “They significantly reduce product labeling time and ‒ most importantly ‒ allow real-time price verification.

“Perovskite photovoltaic cells from Saule Technologies, while being far more efficient than, for instance, the amorphous silicon photovoltaic cells used in calculators, display high efficiency also in artificial light,” added Szewczyk. “As they continue to work efficiently even when the rays of light fall at a big angle ‒ as is the case with pendant lamps ‒ they can supply power to products arranged on lower shelves. In addition, unlike silicon solar cells, they are very thin, light-weight and flexible.”

Szewczyk noted that given these unique properties, perovskite photovoltaic cells do not occupy much space on PESLs, yet they are so efficient that they can power the electronic devices that operate them, including the display and the wireless communication module.

“This enables remotely changing the messages displayed on the label even several times a day, which facilitates, for instance, the sales of products with approaching expiration dates,” added Szewczyk.

Together with the labels, Saule Technologies also provides comprehensive integrated IT and hardware systems using PESL-enabled data transmitters, as well as cloud-based computational and analytical capabilities. Initial PESL technology tests will be carried out in cooperation with Google Cloud Platform.

Szewczyk said that Saule is speaking with many potential clients.

“Demand is bigger than our production possibilities,” added Szewczyk. “We are going to build new, bigger factories. We offer our PESL in a diversified range of shapes, colors and sizes (from 1.54” to 12.5”), equipped with an e-ink (bi- or tri-color) display, a wireless communication module, and a perovskite photovoltaic cell as the power source.

“Along with the price, they can display text and graphics, thus serving as an effective platform for conveying additional messages: advertisements, special discount announcements, loyalty campaigns, and many more. With an option of remotely (wirelessly) modifying of the display content up to 15 times a day, the PESL life span is approximately 10 years. So, it is a very attractive solution for our clients.”