Recently, Fraunhofer-ISE researchers have achieved a conversion efficiency of 68.9% using photovoltaic cells under monochromatic light. This is the highest efficiency achieved so far in the conversion of light energy into electrical energy, and the world record has been refreshed again.
How to create 68.9% efficiency?

ISE uses a thin photovoltaic cell made of gallium arsenide, and a few micrometers thick highly reflective conductive mirror is applied on the back of the semiconductor structure, and the components are irradiated under a 858 nanometer laser.

Gallium arsenide is named III-V solar cell due to its position on the periodic table. Gallium arsenide GaAs battery has always been regarded as the most efficient photovoltaic cell. Its ultra-high photoelectric conversion efficiency allows it to be used in space applications. Commonly used.
Due to the high manufacturing cost of gallium arsenide, ground photovoltaic power plants are rarely used. "Global Photovoltaics" pays attention to a new growth technology called dynamic hydride vapor phase epitaxy (D-HVPE) pioneered by NREL in the past two years. The civilianization of gallium battery costs has seen the dawn of hope.

In terms of power generation principle, researchers introduced that in photovoltaic cells, light absorbed by the battery structure releases positive and negative charges, which are conducted to the back and front of the battery contacts to generate electrical energy. When the energy of the incident light is slightly higher than the inherent band gap energy of the semiconductor material, a photovoltaic effect will occur. Therefore, when a monochromatic laser is used as a light source to match a suitable semiconductor compound material, theoretically high efficiency can be achieved.
It is understood that this thin film method has two obvious advantages in terms of efficiency. First, the photons are captured in the battery, and the energy of the photons near the band gap is maximized, while the transmission loss is minimized, making the battery more efficient. Secondly, the extra photons generated internally through radiation recombination are captured and effectively recovered, which prolongs the effective carrier lifetime, thereby increasing the extra voltage.

About the Fraunhofer-ISE Institute

Fraunhofer-ISE has been conducting cutting-edge research in the photovoltaic field for 40 years. The institute has continuously improved the efficiency of photovoltaic cells through the research of different types of materials, and has made important contributions to reducing the cost of solar power generation. It currently has an area of ​​more than 1,000 square meters. New type of laboratory.
In order to further reduce the area and material usage required for photovoltaic installations, Fraunhofer ISE focuses on stacked photovoltaic power generation, breaking through the traditional efficiency limitations by selectively combining different photovoltaic cell materials.

In August 2020, Fraunhofer-ISE’s III-V/Si tandem photovoltaic cell directly grown on the surface of crystalline silicon set a record of 25.9% efficiency; in April 2021, ISE developed a system made of III-V and silicon semiconductors. The new monolithic laminated battery has created an efficiency record of 35.9%.

At present, new materials like perovskite have also brought new development opportunities. ISE now focuses on optimizing the most promising photovoltaic cell technology to achieve high efficiency and promoting large-scale industrial production of laminated photovoltaics.

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