Researchers developed lead-free photo-battery that could enable users to charge a battery under the sun, without having to plug the device into the wall.
The development of reliable off-grid power supplies is essential to power smart devices and sensor networks. Solar modules need to connect to super capacitors or batteries which increases the cost and complexity of these solutions. Lithium ion photo-batteries can both generate and store energy at the same time. Integrating these functionalities provides simple autonomous power solutions.
Researchers have tried to explore the theoretical potential of photo-batteries. However, the poor interface between photovoltaic materials creates problems with charge transport, greatly reducing the efficiency in comparison to the simple system of a solar cell wired to an external battery.
A research team led by Prof. Jonathan Eugene Halpert, Assistant Professor from the Department of Chemistry at Hong Kong University of Science and Technology (HKUST), has made progress towards efficient photo-batteries using perovskites. They developed an inexpensive, lightweight, and lead-free photo-battery that has dual functions in harvesting solar energy and storing energy on a single device.
The team developed perovskite halide that can harvest energy under illumination without the assistance of an external load in a lithium-ion battery. It does not contain lead, and therefore it is highly stable in air. The team replaced lead with bismuth (Bi), a non-toxic element, forming a strongly light-absorbing crystalline material.
When the lead-free perovskite material is put under light, it absorbs a photon and generates a pair of charges, known as an electron and a hole.
The researchers conducted chrono-amperometry experiments under light and in dark to analyze the increase in charging current caused by the light, and recorded a photo-conversion efficiency rate of 0.428% on photo-charging the battery after the first discharge.
“At present, we plug all our appliances into the wall to charge them. With further development in this field of photo-batteries, we might not have to plug them in at all in the future,” said Prof. Halpert. “We might be able to harvest solar energy and use it to fulfil the power requirements of any devices with modest power needs. Our work is one of the initial steps taken in this field, and, of course, a lot of improvements will be needed to achieve better performance, but we are confident that we can improve its stability and average efficiency with further refinement.”
According to the researchers, the photo-battery can serve as the built-in battery for devices such as smartphones or tablets, and even remote energy storage applications, which can be made easy with these photo-batteries for they are lightweight and portable.