Solar batteries: new material absorbs light, stores energy

Researchers from the University of Cordoba and the Max Planck Institute for Solid State Research (Germany) have made progress on the design of a solar battery made from an abundant, non-toxic and easily synthesised material composed of 2D carbon nitride. Solar batteries combine solar cells that capture light and store its energy in a single device, which then allows the energy to be used when needed.

Alberto Jiménez-Solano, a researcher from the University of Cordoba, explored the design characteristics of the solar battery. Jiménez-Solano said researchers from the Max Planck Institute managed to synthesise a material capable of absorbing light and storing that energy for later use on demand. “It occurred to us to use it to create a solar battery,” Jiménez-Solano said.

To do this, the team first had to find a way to deposit a thin layer of that material (2D potassium carbon nitride, poly(heptazine imide), K-PHI) creating a stable structure to start manufacturing a photovoltaic device due to the fact that that material is normally in powder form or in aqueous suspensions of nanoparticles. That previous work has now allowed researchers to present this solar battery design whereby, combining optical simulations and photoelectrochemical experiments, they are able to explain the characteristics of this device’s high performance when capturing sunlight and storing energy.

The physical structure of the device consists of a high-transparency glass, which has a transparent conductive coating (to allow the transport of load) and a series of layers of semi-transparent materials (with different functionalities), and another conductive glass that closes the circuit. The researchers likened it to a sandwich, made from various layers whose thicknesses have been studied to maximise the level of light absorption and storage.

In this case, the proposed system can absorb light on both sides since it is semi-transparent. The researchers found that rear lighting had certain advantages; something that they managed to elucidate by creating an initial theoretical design in accordance with the experimental restrictions, since this research project will explore experimental limits and come up with feasible designs for these solar batteries. This device could facilitate great versatility, since it makes it possible to obtain a large, one-off current (such as that needed by photography flash) and a smaller current, which could be sustained over time (such as that needed by a mobile phone).

The researchers have demonstrated the performance of this device, made from an abundant, environmentally sustainable material (extracted from urea) which is easy to synthesise. The next steps include continuing to study its operation in various situations outside the laboratory, and adapting it to different manufacturing possibilities and needs.

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