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The future of solar power is about to get a little brighter with new developments in black silicon, a material that can absorb almost the entire spectrum of light – including infrared. Researchers from the Fraunhofer Institute in Germany were recently able to double the efficiency of black silicon solar cells, and the team is also hoping to combine a conventional panel (which can only capture three quarters of the spectrum) with black silicon to create a super-efficient cell that can harness the the full power of the sun.
Scientists at the Fraunhofer Institute in Germany have just succeeded in doubling the efficiency of solar cells made from black silicon. Black silicon is formed by irradiating regular silicon with a laser under sulfuric conditions. The silicon integrates the sulfur into its composition after being treated with the laser pulses, giving the substance its characteristic black color. By changing the shape of the laser beams, the researchers were able to overcome one of the most common problems of working with silicon.
In normal silicon, infrared does not possess enough energy to excite the electrons in the conduction band necessary to generate electricity. By incorporating sulfur, an intermediate level is formed in the atomic lattice. This level acts as a step for electrons to jump to the conduction band as well as move in reverse from the band. However, energy is still lost when electrons move backwards from the conduction band. “We used the laser pulses to alter the embedded sulfur in order to maximize the number of electrons that can climb up while minimizing the number that can go back down,” said Dr. Stefan Kontermann, one of the researchers involved in the project.
Prototypes of the improved black silicon cells are already in production, and engineers are also working on a new, tandem solar cell created by removing the black covering of a standard solar cell and and applying the black silicon. This hybrid could increase efficiency by at least one percent. The Fraunhofer Institute is also in the process of developing the laser system for mass production so that manufacturers can simply add the equipment to their assembly line and make black silicon for themselves.
+ The Fraunhofer Institute