Indoor solar cells for smart connected devices
A new type of dye-sensitised solar cells harvests light from indoor lamps in the visible spectrum with up to 34 % efficiency.
The Internet of Things, or IoT, refers to a network of physical devices and applications connected through the internet. It is estimated that by 2025, many facets of our lives will be mediated through 75 billion IoT devices, a majority of which will be located indoors. Broad installation of such IoT devices requires the devices to become autonomous, meaning that they should no longer need batteries or a grid connection to operate. To achieve this, it is crucial to identify a local low-maintenance energy source that can provide local power to IoT devices, especially in ambient conditions.
A research team led by Marina Freitag, assistant professor at the Department of Chemistry, Uppsala University in Sweden, has developed new indoor photovoltaic cells that can conver up to 34 percent of visible light into electricity to power a wide range of IoT sensors. The team has designed novel dye-sensitised photovoltaic cells based on a copper-complex electrolyte, which makes them ideal for harvesting indoor light from fluorescent lamps and LEDs. The latest promising results establish dye-sensitised solar cells as leaders in power conversion efficiency for ambient lighting conditions, outperforming conventional silicon and solar cells made from exotic materials.
"Knowing the spectra of these light sources makes it possible to tune special dyes to absorb indoor light. While generating large amounts of energy, these indoor photovoltaics also maintain a high voltage under low light, which is important to power IoT devices", says Freitag.
In cooperation with the Technical University of Munich, the researchers have further designed an adaptive system that works as a power management for solar-powered IoT sensors. In contrast to their battery-limited counterparts, the light-driven devices intelligently feed from the amount of light available. Computational workloads are executed according to the level of illumination, minimising energy losses during storage and thus using all light energy to the maximum of its availability.
In the future, scientists expect that billions of IoT devices self-powered by indoor solar cells will provide everything from environmental information to human-machine and machine-machine communications. Such advanced sensors can further enhance the next wave of robotics and autonomous systems currently in development.
[Hannes Michaels, Michael Rinderle, Richard Freitag, Iacopo Benesperi, Tomas Edvinsson, Richard Socher, Alessio Gagliardi, Marina Freitag, Dye-sensitized solar cells under Ambient Light Powering Machine Learning: Towards autonomous smart sensors for the Internet of Things, Chemical Science, 2020, DOI: 10.1039/C9SC06145B]