An international research team applied a new type of composite material to simplify the manufacturing steps of silicon solar cells and increase the photoelectric conversion efficiency of undoped silicon cells to 19%.

At present, the main material of most solar panels is crystalline silicon. The crystal itself or the deposited layer on the crystal will be doped with some other metal atoms. These atoms can combine with silicon atoms to generate electrons, but also can selectively generate electron holes. In both cases, the conductivity of the crystal can be enhanced. The conversion efficiency of the doped crystalline silicon solar cell can exceed 20%, while the efficiency of the undoped cell never exceeds 14%.

The doping process can increase the solar energy conversion efficiency, but it will increase the complexity of the semiconductor device and reduce its performance, which will hinder the subsequent manufacturing process. The special mixed materials in the new research can omit the doping process, and only need 7 simple steps to combine the new materials and simple coating processes to improve efficiency. As a visiting scholar at the Lawrence Berkeley National Laboratory of the U.S. Department of Energy and the University of California, Berkeley, James Bullock published relevant results in Nature Energy as the first author. He said: "The structure of the solar cells we make is very Simple and can effectively reduce costs."

In this study, the research team coated a thin layer of molybdenum oxide on the silicon wafer side of the solar cell facing the sun, and used lithium fluoride on the back. Both coatings are only tens of nanometers thick and both are transparent. They have complementary electronic structures and are very suitable for solar cells.

Another member of the research team, Steven de Wolfe, said that the team discovered the effectiveness of molybdenum oxide several years ago. After the combination, the molybdenum oxide performed very well, making a surprising change to the standard process for making crystalline silicon solar cells.

The research team hopes that it can continue to test more materials to see if there are better materials to improve conversion efficiency.

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