| Aug 03, 2022 |
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(Nanowerk News) Solar cell technologies have been improving incrementally over the decades, but energy conversion has remained less than optimal.
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Now, researchers at Kyoto University have developed a novel wafer bonding technology using an optical upconversion material that transforms sunlight to shorter-wavelengths. This new semiconductor process utilizes the interface’s optical function for bond formation (Applied Physics Letters, “Upconversion semiconductor interfaces by wafer bonding for photovoltaic applications”).
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| Semiconductor bonding mediated by upconversion material. (Image: Katsuaki Tanabe, Kyoto University)
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The team created a stacked structure consisting of a thin silicon film mimicking the upper subcell of a multi-junction solar cell and a silicon solar cell wafer; these layers were bonded with an adhesive made from upconversion nanoparticles dispersed in a hydrogel.
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Conventional multi-junction solar cells are created with the vapor phase growth method. However, this method is limited by lattice matching in semiconductor materials.
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The team, led by Katsuaki Tanabe, has applied their wafer bonding method to the production of a range of optical and electronic devices, demonstrating that different semiconductor materials can be stacked in any combination without the restriction of lattice matching.
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“Even inherently non-absorbed light of longer wavelengths in the lower subcell of a multi-junction solar cell could be used to enhance the efficiency of the overall energy conversion via our upconverting interface,” concludes the author.
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