| Work Detail |
Scientists at the Max Planck Institute for Solid State Research have developed a bifunctional solar battery device that simultaneously enables light charging, charge storage, and electrical discharge.
Solar batteries, which combine solar cells and batteries in a single device, are a novel decentralized and integrated approach to renewable energy supply. This design is proposed to minimize losses caused by charging removal from the solar cell, wiring, and voltage or current mismatches.
Researchers at the Max Planck Institute for Solid State Research (Germany) have studied the optical design characteristics of a solar battery based on the cheap and abundant 2D polymeric carbon nitride as a photoanode.
To do this, the team first had to find a way to deposit a thin layer of 2D potassium carbon nitride, poly(heptazine imide), K-PHI, which typically occurs as a powder or in aqueous suspensions of nanoparticles. They then carried out optical simulations and experiments to take a closer look at the efficiency limitations and design considerations of their solar battery.
Being semi-transparent, the solar battery can absorb light from both sides. Specifically, it sandwiches a series of layers of semi-transparent materials with different functionalities between two layers of highly transparent conductive glass.
By calculating the absorbance inside the solar battery comprising different thicknesses of K-PHI active layer and the corresponding layer of polystyrene sulfonate void storage material, the researchers found that illumination through the rear of the device is superior regardless of the thickness of the active layer, provided that the pickup layer is thinner than the active layer.
They also found that thinner active layers lead to higher photocharge currents (better solar cell functionality), but lower electrical capacity (poorer battery functionality).
The research team also reported that their device shows great versatility. It allows for both large, spot currents and smaller currents, which could be sustained for longer, typical of mobile phone requirements.
“We show how power output increases most significantly for small electrical discharge currents that are in the range of the photocharge current generated by illumination. This leads us to conclude that only small increases in light intensity can lead to large increases in performance,” the researchers write in “ Bridging the gap between solar cells and batteries: Optical design of bifunctional solar batteries based on 2D carbon nitrides ” ( Bridging the Gap Between Solar Cells and Batteries: Optical Design of 2D Carbon Nitride-Based Bifunctional Solar Batteries), published in Advanced Energy Materials .
They add that the results presented in the paper are transferable to other solar battery concepts, such as photocapacitors or redox flow solar batteries, which use bifunctional electrodes or have separate heterojunctions of light-absorbing and charge-storing materials. |
