Semitransparent solar cells for solar windows

Korean scientists have developed a semitransparent solar cell that is said to be highly efficient and functions as a thermal mirror.

Solar cells are typically made of crystalline silicon, which is difficult to make translucent. By contrast, semitransparent solar cells use, for example, organic or dye-sensitised materials. But compared to crystalline silicon-based cells, their power-conversion efficiencies are relatively low. Perovskites are hybrid organic-inorganic photovoltaic materials, which are cheap to produce and easy to manufacture. They have recently received much attention, as the efficiency of perovskite solar cells has rapidly increased to the level of silicon technologies in the past few years.

Using perovskites, a Korean research team, led by Professor Seunghyup Yoo of the Korea Advanced Institute of Science and Technology and Professor Nam-Gyu Park of Sungkyunkwan University, has developed a semitransparent solar cell that is highly efficient and functions very effectively as a thermal mirror.

The Korean team developed a ‘top transparent electrode’ (TTE) that works well with perovskite solar cells. The TTE is based on a multilayer stack consisting of a metal film sandwiched between a high refractive index layer and an interfacial buffer layer. This TTE, placed as a solar cell’s top-most layer, can be prepared without damaging ingredients used in the development of perovskite solar cells. Unlike conventional transparent electrodes that only transmit visible light, the team’s TTE plays the dual role of allowing visible light to pass through while at the same time reflecting infrared rays.

The semitransparent solar cells made with the TTEs exhibited an average power conversion efficiency of 13.3%, reflecting 85.5% of incoming infrared light. Currently available crystalline silicon solar cells have up to 25% efficiency but are opaque.

The team believes that if the semitransparent perovskite solar cells are scaled up for practical applications, they can be used in solar windows for buildings and automobiles, which not only generate electrical energy but also allow smart heat management in indoor environments, thereby using solar energy more efficiently and effectively.