The new class of monolithically integrated, portable PV-battery systems (SiPV-LIBs) power source is designed to work under sunlight and indoor lighting and could power electric devices even in the absence of light.
"This device provides a solution to fix both the energy density problem of batteries and the energy storage concerns of solar cells," says Professor Sang-Young Lee.
"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 and storage system for use in electric vehicles and portable electronics."
Based on miniaturised crystalline Si photovoltaics (c-Si PVs) and printed solid-state LIBs with a bipolar cell configuration, the device uses a thin-film printing technique, in which the LIB is directly printed on the aluminium electrode of a c-Si PV module.
To enable the seamless electrical connection of the two different energy systems, the Al metal layer is simultaneously used as a current collector of the LIB, as well as an electrode for solar cells. This allows the battery to be charged without the loss of energy.
The team successfully implemented lossless c-Si PV modules by designing rear electrode-type solar cells.
According to the researchers, the device was capable of fully charging under sunlight illumination after only 2min. It also showed decent photo-rechargeable electric energy storage behaviour at temperatures up to 60°C and at a low light intensity of 8mW/cm2.