How Windows of Tomorrow Will Generate Electricity

A new study by scientists at Incheon National University in Korea shows how to make a fully transparent solar cell.

In a new study published in Journal of Power Sources, an international team of researchers, led by Professor Joondong Kim from Korea, demonstrate the first transparent solar cell. Their innovative technique is based on a specific part of the solar cell: the heterojunction, made up of thin layers of materials responsible for absorbing light. By combining the unique properties of titanium dioxide and nickel oxide semiconductors, the researchers were able to generate an efficient and transparent solar cell.

Five years after the Paris climate agreement, all eyes are on the world’s progress on the path to a carbon-free future. A crucial element of this objective concerns the energy transition from fossil fuels to renewable sources, such as solar, hydro, wind and wave energy. Among these, solar energy has always held the greatest hope in the scientific community, as the most reliable and abundant source of energy on Earth. Over the past decades, solar cells have become cheaper, more efficient and more environmentally friendly. However, current solar cells tend to be opaque, preventing their wider use and integration into everyday materials, forced to line up on rooftops and in remote solar farms.

But what if next-generation solar panels could be integrated into windows, buildings, or even cell phone screens? This is the hope of Professor Joondong Kim from the Department of Electrical Engineering at Incheon National University, Korea. In a recent study published in Journal of Power Sources, he and his colleagues detail their latest invention: a fully transparent solar cell. “The unique characteristics of transparent photovoltaic cells could have various applications in human technology,” explains Professor Kim.

The idea of ​​transparent solar cells is well known, but this new application where scientists have been able to translate this idea into practice is a crucial new discovery. Currently, the materials that make the solar cell opaque are semiconductor layers, those responsible for capturing light and translating it into electric current. Therefore, Professor Kim and his colleagues examined two potential semiconductor materials, identified by previous researchers for their desirable properties.

The first is titanium dioxide (TiO2), a well-known semiconductor already widely used to make solar cells. In addition to its excellent electrical properties, TiO2 is also an environmentally friendly and non-toxic material. This material absorbs UV light (part of the light spectrum invisible to the naked eye) while letting most of the visible light range through. The second material studied to make this junction was nickel oxide (NiO), another semiconductor known to have high optical transparency. As nickel is one of the most foggy elements on Earth and its oxide can easily be made at low industrial temperatures, NiO is also an excellent material for making environmentally friendly cells.

Reference: “Transparent photovoltaic cells and photodetectors self-powered by TiO₂/ NiO heterojunction ”by Thanh Tai Nguyen, Malkeshkumar Patel, Sangho Kim, Rameez Ahmad Mir, Junsin Yi, Vinh-Ai Dao and Joondong Kim, September 12, 2020, Energy sources log.
DOI: 10.1016 / j.jpowsour.2020.228865