Transparent Solar Glass Cells Achieve Innovative High Energy Efficiency. Building's Reliance on Glass Windows for Power Generation May Become a Reality

A research team from the University of Michigan has created a new energy efficiency record for transparent solar cells, bringing the dream of glass curtain walls in skyscrapers becoming their own source of energy one step closer to reality.

This new type of transparent solar cell adopts organic or carbon based design instead of traditional silicon materials, achieving a conversion efficiency of 8.1% and a transmittance of 43.3%. Although this type of battery may appear slightly green, it is still transparent, just more like the gray of sunglasses and car windows.

Using Organic Materials, Customizable According to Latitude

Imagine in the future, skyscrapers will be covered with photovoltaic glass cells. When sunlight shines on the photovoltaic glass, the light will be converted into electricity, which will converge in the control room and provide power to the entire building.

Obviously, the advancement of transparent solar cells can make solar energy more cost-effective overall, as this study combines the cost of glass in photovoltaics, which is the most expensive part of photovoltaic modules, with the cost of installing windows in buildings.

Li Yongxi, an assistant research scientist at the University of Michigan, said that most solar windows on the market today are made of inorganic silicon-based materials, while newly developed solar windows are made of organic, carbon based, and hydrogen based materials.

Compared with inorganic materials, organic materials have many advantages. For example, silicon materials are very heavy, while organic materials have low density and light weight, "said Li Yongxi.

The glass curtain walls of skyscrapers usually have a layer of coating that can reflect and absorb some light in the spectral and near-infrared regions, thereby reducing brightness and heat inside the building. Transparent solar cells can utilize these energy sources to reduce the electricity demand inside skyscrapers.

This new material is designed to be transparent in visible light and absorb energy in the near-infrared region. The near-infrared region is the invisible part of the spectrum, accounting for a significant portion of solar energy. In addition, researchers have developed optical coatings to enhance the energy generated by infrared light and transparency in the visible light range.

The neutral color version of this transparent glass battery is made with indium tin oxide electrodes. If silver electrodes are used, the conversion efficiency can be increased to 10.8% and the transparency can be increased to 45.8%. However, the latter's slightly green tone may not be accepted in certain application scenarios.

At present, both versions can be mass-produced using materials that are less toxic than other transparent solar cells. This type of transparent solar cell can also be customized according to the latitude of the location, as their efficiency is highest when sunlight shines on them at a vertical angle. This battery can be placed between double-layer glass windows.

Is It 'Fantasy' or Excessive Hype?

Although Li Yongxi and his team have achieved what Wheeler called "wonderful" efficiency and transparency, there are also doubts about whether there are solar windows on the market that have reached similar milestone heights. For example, Ubi uous Energy Inc., a technology startup based in Silicon Valley, stated that they developed a transparent solar cell with a conversion efficiency of 9.8% and transparency of 38.3% last year. "It should be noted that this is not a record breaking performance," Richard Lunt, co-founder of the company and professor at Michigan State University, said in an email.

Wang Xiaoting, an energy expert from Bloomberg New Energy Finance's solar energy team, also questions the importance of researching this type of organic solar window. Wang Xiaoting said that although organic photovoltaics seem to be energy-saving compared to other organic modes, they typically perform the worst among all available photovoltaic products.

All transparent solar windows, whether organic or inorganic, still need to overcome many limitations in terms of durability. For example, compared to replacing opaque rooftop solar panels, the cost of replacing solar windows at the end of their lifespan may be very high.

If you want to use solar glass cells to decorate the entire facade of a skyscraper, it is best to ensure that it can be used for a long time, as replacing this giant solar panel will be a huge challenge.