The results of the research, supported by a grant from the Russian Science Foundation (RSF), were published in the journal Applied Physics Letters.

Researchers from the Skolkovo Institute of Science and Technology and the National Research University Higher School of Economics have developed a photoelement that converts artificial light into electricity to power a wireless temperature and humidity sensor. It is made from perovskite – a lightweight, thin, relatively cheap material used to create solar cells.

As scientists told Izvestia, many devices we use in everyday life can operate without direct human involvement. For example, a smart humidifier turns on when indoor humidity drops, and an air conditioner maintains the required temperature. However, for such devices to work, a large number of sensors are needed: in the case of a humidifier and air conditioner, these are humidity and temperature sensors, respectively.

Typically, conventional batteries are used to power such sensors. However, these power sources are harmful to the environment: they contain mercury, lead, cadmium, and other hazardous substances. Furthermore, batteries are difficult to recycle and can only be used once, unlike accumulators (rechargeable batteries). For example, smartphone batteries typically withstand 500 to 1000 charge cycles before their capacity drops. And they have a significant drawback – they need to be regularly recharged. Replacing batteries and recharging accumulators consumes a lot of resources, especially when there are thousands of such sensors.

To protect the device from moisture, chemicals, and other external influences, thereby extending its service life, scientists enclosed the developed photoelement in a polymer shell that is resistant to solvents and acids, has a high melting point, and does not conduct electricity. At the same time, the authors proved that this encapsulation method extends the lifespan to at least 10,000 hours, which is already comparable to the operating time of disposable batteries in IoT sensors.

Tests of the prototype showed that for uninterrupted operation for up to 87 hours, the photoelement requires room illumination of about 1000 lux (lx). Typically, in office buildings, this indicator, measured at the desktop surface, is precisely 800-1000 lx. For the device to not require recharging at all, 3000 lx or higher is needed. Such high illumination indoors occurs near an operating artificial light source, such as office lamps, so researchers recommend installing the sensor as close to it as possible.

“In this work, we demonstrated that perovskite-based photoelements, with proper protection from the environment, can effectively perform the function of a charger for wireless sensors. This opens up new possibilities for their application, using them not only for converting solar energy but also artificial lighting. In the future, we plan to develop a photoelement integrated with a supercapacitor as a single device,” said the project leader, research scientist at the Skoltech Center for Energy Science and Technology, Alexandra Boldyreva.

The research clearly demonstrates that perovskite photovoltaics is an extremely promising direction for autonomous power supply of electronics, ITMO University professor, head of the Laboratory of Hybrid Nanophotonics and Optoelectronics, Sergey Makarov, told Izvestia. Its key advantage is revealed under low light conditions, where traditional silicon photoelements have extremely low efficiency.

“It is important to note that indoors, the operating conditions for perovskite elements are much less aggressive than outdoors, which significantly increases their durability when using optimized encapsulation, as in this work. Demonstrating the powering of a sensor from room light is a serious step towards the commercialization of the technology. We expect that in the near future, many wearable devices and Internet of Things sensors will become completely energy-independent by being equipped with such perovskite photoelements. Thus, this work paves the way for creating environmentally friendly, self-powered sensor networks,” the scientist said.

This is a promising direction; it is becoming one of the niches where perovskite has real advantages over silicon due to strong absorption and low defect concentrations, noted Danila Saranin, Dr. Sc. (Tech.), head of the Laboratory of Advanced Solar Energy at MISIS University.

“MISIS University has long been conducting comprehensive developments in this area. Our solar panels hold a record for Russia and the EU, with an efficiency of 36% for converting warm LED light. And back in 2020, we won the Innovator of Moscow award for developing a full-fledged power unit based on perovskites to charge any gadget from dim office light,” the specialist noted.