Schematic representation of the monolithically integrated SiPV–LIB device and the electrochemical performance of the bipolar LIB. Credit: UNIST

A new power source may lead to a quicker charge for portable electronics.

A team of researchers from the Ulsan National Institute of Science and Technology (UNIST) in South Korea have developed a single-unit, photo-rechargeable portable power source that is designed to work under sunlight and indoor lighting, allowing users to power portable electronics anywhere with access to light.

The power source is based on high-efficiency silicon solar cells and lithium-ion batteries (LIB).

The single-unit PV-LIB device exhibits improved photo-electrochemical performance and its compact design lie beyond those achievable by conventional PVs or LIBs alone. The device was able to rapidly charge in less than two minutes with a photo-electric conversion/storage efficiency of 7.61 percent, a large improvement in photo-charging.

The device, which uses a thin-film printing technique where the solid-state lithium ion battery is directly printed on the high-efficiency miniaturized crystalline Si photovoltaics (c-Si PV) module, represents a new class of monolithically integrated, portable PV-battery system based on miniaturized crystalline Si photovoltaics and printed solid-state lithium-ion batteries.

“This device provides a solution to fix both the energy density problem of batteries and the energy storage concerns of solar cells,” professor Sang-Young Lee, said in a statement. “More importantly, 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.”

Through an in-series printing process the researchers were able to fabricate a solid-state LIB with a bipolar cell configuration directly on the aluminum electrode of a c-Si PV module.

The battery can be charged without the loss of energy because the researchers enabled the seamless architectural/electrical connection of the two different energy systems where the aluminum metal layer is simultaneously used as a current collector of the LIB as well as an electrode for solar cells.

They designed rear electrode-type solar cells to successfully implement lossless c-Si PV modules.

By inserting the SIPV-LIB device into a pre-cut credit card the researchers were able to fabricate a monolithically integrated smartcard.

They then drew electric circuits on the back of the credit card using a commercial Ag pen to connect the device with an LED lamp and they also electrically connecting the device with a smartphone or MP3 player and explored its potential application as a supplementary portable power source under sunlight illumination.

The device fully charged under sunlight illumination after just two minutes, while also showing ‘decent’ photo-rechargeable electric energy storage behavior even at high temperatures in extremely low light intensity.

“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 said.

The study was published in Energy & Environmental Science