| Summary: | 碩士 === 國立交通大學 === 光電工程學系 === 100 === We have fabricated silicon-based alloy tandem thin film solar cell by using high density plasma method. And optimize the tandem thin film solar by using tunneling-recombination junction and high hydrogen ratio bottom absorption layer.
Due to high optical band gap of amorphous silicon thin film, a-Si thin film solar cell shows the property of high open circuit voltage. But, this feature also limit the absorption in the near infrared part of solar spectra, so the short circuit current density is much lower compared with amorphous silicon germanium alloy thin film silicon solar cell. In order to overcome the above-mentioned shortcomings, we utilize the amorphous silicon germanium alloy a-SiGe (band gap 1.4~1.6eV) to engineer the optical bandgap. The thin films with different optical bandgap could absorb the different part in solar spectra. Thus, we can effectively take advantage of the full solar spectra. And we can also develop muti-junction thin film solar cell based in the thin film solar cells. Each junctions of muti-junction solar cell have different optical bandgap, so they could absorb different part of solar spectra.
Currently, we have demonstrated single junction a-Si, a-SiGe thin film solar cell with conversion efficiency achieving 9.2% and 5.7%, respectively. Compared with a-si thin film solar cell, the quantum efficiency of a-SiGe significantly increased in 650~800nm. Besides, we have also demonstrated double junctions solar cell, including a-Si/a-Si and a-Si/a-SiGe tandem solar cell. The open circuit voltage of a-Si/a-Si, a-Si/a-SiGe tandem solar cells is 1.69V, 1.46V respectively. The muti-junction we mentioned above have successful performance in open circuit voltage. Conversion efficiency of a-Si/a-Si and a-Si/a-SiGe tandem solar cell is 8.8% and 6.3% respectively. In the future, my research will focus on tunneling junction between each interface and film quality of each kind silicon based alloy to obtain the triple-junction thin film solar cell with high conversion efficiency.
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