By Jon Gabay, contributing editor
It was pretty astounding when LCD and solar cell technology came together with microprocessors to allow solar- and light-powered calculators to work. It actually was a milestone when a technology could be designed to function virtually forever. Real-time energy intake could be more than enough to power sophisticated electronics ad displays with a user interface.
A recent report announced a new all-in-one photo-rechargeable portable power source — which is a fancy way to say a new class of super-efficient, solar-powered battery systems that can charge in either sunlight or indoor light. The prototype device, dubbed the SIPV-LIB, relies on paper-thin solid-state lithium-ion batteries that are directly printed on miniaturized crystalline Si photovoltaics (c-Si OVs). Developed by Professor Sang-Young Lee and Professor Kwanyoung Seo of Energy and Chemical Engineering at UNIST (Ulsan National Institute of Science and Technology), the device is the next step in solar-powered technology. According to Professor Lee in the Institute’s press release, “This device provides a solution to fix both the energy density problem of batteries and the energy storage concerns of solar cells.”
What the team has done is to use miniature silicon crystals and deposit them as the top layer of a printed lithium-ion battery. An aluminum electrode lies in between the silicon crystals and the battery, serving as a common electrode between the two and also acting as a charge collector. The silicon crystals create a photovoltaic cell whose charge gets transferred to the lithium-ion battery, according to the development team.
Using a single-junction solar cell design, Professor Seo and his team implemented this rear-electrode configuration and demonstrated what they describe as “lossless c-Si PV modules.” Another benefit of using this configuration is that the architecture can be used to fabricate small solar cells formed on single silicon substrates, subsequently simplifying the manufacturing process. But there’s more: Rear-electrode-type design may prevent the energy loss experienced with traditional single-cell photovoltaic module designs. And still another benefit of the architecture is that its use of a lithium-ion battery in solid-state form can potentially overcome any danger concerns that have been carried over from older lithium-ion battery designs.
The all-in-one unit exhibits good performance so far. Each individual cell charges in less than two minutes with a photoelectric conversion ration of 7.6%. This was demonstrated by fabricating a monolithically integrated smart card. An SIPV-LIB was inserted into a cutout of a credit card and wired to an LED lamp (see below).
Rapid-recharge is fastest in direct sunlight, which provides almost a full charge in less than two minutes. Thin demonstrations like the LED on a credit card allow testing and demonstrating what this technology can do so far.
The team tested this configuration so far up to 60°C. They also tested under low-light conditions of 8 mW/cm2 , or the equivalent of a dimly lit room. Testing has also been performed with the SIPV-LIB attached to smartphones and MP3 players, and the results promise that this technology will work in many applications.
And this is just the beginning.
While it is unknown at this time how efficient this technology can become, because this is still a rapidly evolving technology, “The SiPV–LIB device presented herein shows great potential as a photo-rechargeable mobile power source that will play a pivotal role in the future era of ubiquitous electronics,” Lee predicts in his paper published in the journal Energy & Environmental Science. The batteries “have relatively high power and energy densities under direct sunlight, which demonstrates its potential application as a solar-driven infinite energy conversion/storage system for use in electric vehicles and portable electronics.”
Source: Unist , Pubs.rsc.org , and Phys.org
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