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▲ [15p-P13-1] Fabrication of low B-doped p-BaSi2/n+-Si heterojunction solar cells
Keywords:semiconductor, solar cell, silicide
Semiconducting BaSi2 has attracted attention as a future absorber-layer material for thin-film solar cells. It has an indirect band gap of approximately 1.3 eV, matching the solar spectrum, and has large absorption coefficients, reaching 3.0×104 cm-1 at 1.5 eV. We have successfully fabricated n-Si/B-doped p-BaSi2 heterojunction solar cells that achieved a conversion efficiency of 9.9%. In the work mentioned, B-doped p-BaSi2 (p = 2.2 × 1018 cm-3) with an optimum thickness of 20 nm acts as a hole transport layer. The deterioration of in thicker p-BaSi2 layers is suspected due to the small minority-carrier lifetime τ of p-BaSi2. In previous work, we confirmed that τ strongly depends on the hole concentration p of p-BaSi2. We measured that low doped p-BaSi2 with p=1.4×1016 cm-3 has a τ of 2.0 ms, two orders higher than sample with p=3.9×1018 cm-3. In order to utilize B-doped p-BaSi2 as an active layer, we need to employ n-Si with lower resistivity (higher electron concentration n), so that the depletion region stretches toward the p-BaSi2 layer, and that the device has a sufficient built-in potential at the junction.
In this work, we fabricated 300-nm-thick low- doped p-BaSi2 on the Si substrates with various resistivities and examined the electrical properties using J-V characteristics. We then evaluated the result from the crystallinity point of view.
In this work, we fabricated 300-nm-thick low- doped p-BaSi2 on the Si substrates with various resistivities and examined the electrical properties using J-V characteristics. We then evaluated the result from the crystallinity point of view.