Car windows, mobile screens for battery charging

Scientists have developed a new method that can directly charge a battery from a smartphone screen. Developed by a research team affiliated with UNIST, the method can directly provide energy from the glass of buildings, cars and mobile devices via transparent solar cells.

The new type of transparent solar cells and modules is characterized by high efficiency while retaining the properties of glass, being colorless and transparent.

The transparent solar cell achieved colorlessness and transparency by introducing an “all-back-contact” design that places all the components of the solar cell on the back. It achieved the high efficiency and aesthetics that transparent solar cells must have at the same time.

The transparent cellular module has high efficiency

The material was developed by Professor Kwanyong Seo and his research team from the School of Energy and Chemical Engineering at UNIST.

This method, called Seamless Modularization technology, eliminates gaps between devices without using metal wires. In the existing modularization method, a gap between devices and opaque metal wires solved the problem of destroying the aesthetics of transparent solar cells.

The newly developed 16 cm² transparent solar cell module has high efficiency ranging from 20% to 14.7% in transmittance while maintaining aesthetics similar to a single device. It also managed to charge a smartphone using natural sunlight. It also proved the feasibility of using the screen of a small mobile device as a power source, according to a study conducted at UNIST.

Transparent solar cells can be used in buildings, car windows

“This study fundamentally solved the aesthetic problem of the existing modular solar cell construction method by designing a new device structure,” said researcher Jeonghwan Park and assistant professor Kangmin Lee.

“This has opened up the possibility of using transparent silicon solar cells in various industries, for example in the production of small appliances, as well as in construction and automotive glass production.

Seo said the study opens a new avenue for modularity research, which is essential for commercializing transparent silicon solar cells.

“We plan to continue research so that transparent solar cells can become a key technology in the environmentally friendly energy industry of the future,” Seo added.

Published in the international journal Proceedings of the National Academy of Sciences (PNAS), the all-back-contact (ABC) design not only demonstrates high power conversion efficiency (PCE) in solar cells but also provides unobstructed visibility through transparent solar modules. Remarkably, the transparent c-Si ABC solar cells achieved a peak PCE of 15.8% while maintaining an average visible transmission of 20%.

By seamlessly connecting the unit cells, the output voltage and power were systematically tuned from 0.64 V and 15.8 mW (for a 1 cm2 unit cell) to 10.0 V and 235 mW (for a 16 cm2 module). In addition, according to the study, we successfully demonstrated photocharging of a smartphone using the ABC transparent solar module.