- Fraunhofer ISE has claimed to have improved efficiency of a four-junction III-V solar cell to 47.6%
- It is an improvement over 46.1% efficiency reported by the institute along with French semiconductor materials maker Soitec in 2016
- They were able to increase the efficiency by using an improved contact layer and a 4-layer anti-reflection coating
German photovoltaic research institute Fraunhofer Institute for Solar Energy Systems (ISE) has achieved 47.6% efficiency for a four-junction III-V solar cell, using a new anti-reflection coating calling it the world’s most efficient solar cell.
This is an increase from its previous high of 46.1% on a cell whose layer structure it developed in 2016 with French manufacturer of semiconductor materials, Soitec Inc, which in the past tried to commercialize CPV modules based on technology developed at ISE (see CPV On Record).
The researchers explain that the upper tandem cell is made up of allium indium phosphide (GaInP) and aluminum gallium arsenide (AlGaAs), which was bonded by Soitec onto a lower tandem solar cell made of gallium indium arsenide phosphide (GaInAsP) and gallium indium arsenide (GaInAs).
While the top later of GalnP absorbs short-wave sunlight in the visible spectral range, the lower 3 layers convert infrared light.
To this combination, they applied an improved contact layer and a 4-layer anti-reflection coating to bring down resistance losses on the front side of the cell within a broad range of 300 nanometers to 1,780 nanometers. In comparison, they explain, conventional silicon solar cells can absorb sunlight only up to a wavelength of 1,200 nanometers.
Prof. Dr. Stefan Glunz, Division Director of Photovoltaics Research at Fraunhofer ISE, believes, “With tandem photovoltaics, it is possible to leave the limitations of single-junction solar cells behind and ultimately achieve a reduction in solar power costs.”
Researchers see possible applications of these highly efficient tandem solar cells in concentrator photovoltaic systems that can contribute to efficient power generation in sun-rich countries.
The research work has been carried out under a German government funded 50 Percent project that aims to develop a cell with 50% efficiency for the 1st time for which the team keeps optimizing each individual layer.
Recently, the National Renewable Energy laboratory (NREL) of the US announced 39.5% efficiency for a triple-junction solar cell using standard-1 sun conditions, and claiming it to be the highest efficiency solar cell of any type (see 39.5% Efficiency For Triple-Junction Solar Cells).