The emergence of solar cells that can produce electricity while maintaining high transparency is expected to have a major ripple effect in the smart city and eco-friendly energy markets.

UNIST Department of Energy and Chemical Engineering Professor Yang Chang-deok's team announced on the 15th that they have developed a semitransparent organic solar cell that can utilize windows or mobile device screens as a 'transparent power plant.'

In this study, a solar cell was developed that recorded a photoelectric conversion efficiency of over 10.81% and a visible light transmittance of 45.43%, dramatically improving the dark appearance problem of existing solar cells while suggesting the possibility of producing electricity while maintaining high transparency.

Solar cells are usually installed on roofs or roadsides and appear dark because they absorb sunlight and convert it into electricity.

On the other hand, for objects to appear transparent, sunlight must pass through them, and it was quite difficult to satisfy these two functions at the same time.

Accordingly, Professor Yang Chang-deok's team developed a high-performance photoactive layer that selectively absorbs only the invisible infrared band while allowing about 45% of visible light among sunlight to pass through.

The '4FY' receptor molecule synthesized by the research team is symmetrical to the ADA structure, but has a structure between fluorine and hydrogen, and fluorine and sulfur.It is designed to induce local asymmetric interactions.

This molecular structure design improves the alignment between molecules to secure a charge transfer path, further increasing cell efficiency and demonstrating durability that is approximately 17 times better than that of existing Y6 receptor-based semitransparent solar cells.

“Asymmetry often increases battery efficiency while also causing problems such as shortened battery life, so we introduced local asymmetry to create a molecular structure that takes advantage of both sides,” explained first author Yang Sang-jin.

Additionally, the research team demonstrated high durability, maintaining most of the initial performance for a total of 134 hours in a 'dial cycle stability test' that simulates an outdoor environment with day and night repeat conditions.

These achievements demonstrate that semitransparent organic solar cells can be applied to a variety of real-life applications, such as building windows, smartphone protective films, and transparent displays.

Professor Yang Chang-deok said, “The semitransparent solar cell developed by our research team is a new type of solar cell that produces electricity by utilizing invisible infrared energy.” He added, “In the future, instead of the existing dark solar cells, we expect to be able to produce electricity from the screens of buildings or mobile devices with a transparent power plant concept.”

The results of this study were published on June 10 in the international academic journal Angewandte Chemie International Edition, and were conducted with support from the Ministry of Science and ICT, the National Research Foundation of Korea, the Ministry of Trade, Industry and Energy, and the Korea Institute of Energy Technology Evaluation and Planning.