Abstract
Stopping the plasma-enhanced chemical vapor deposition (PECVD) once and maintaining the film in a vacuum for 30 s were performed. This was done several times during the formation of a film of i-layer microcrystalline silicon (μc-Si:H) used in thin-film silicon tandem solar cells. This process aimed to reduce defect regions which occur due to collision with neighboring grains as the film becomes thicker. As a result, high crystallinity (Xc) of μc-Si:H was obtained. Eventually, a solar cell using this process improved the conversion efficiency by 1.3% (0.14 points), compared with a normal-condition cell. In this paper, we propose an easy method to improve the conversion efficiency with PECVD.
Highlights
Stable high quality hydrogenated microcrystalline silicon films which are used in thin-film silicon tandem solar cells have been difficult to make since the quality of μc-Si:H varies depending on its underlying shape or film thickness [1]
This is because a defective component in the μc-Si:H film is affected by transparent conductive oxide (TCO) texture, as the film thickness of the microcrystalline silicon increases [2]
Eff improved by 1.3% (0.14 points), Voc by 0.011 V, and fill factor (FF) by 0.002 compared with those for the normal-condition cell
Summary
Stable high quality hydrogenated microcrystalline silicon (μc-Si:H) films which are used in thin-film silicon tandem solar cells have been difficult to make since the quality of μc-Si:H varies depending on its underlying shape or film thickness [1]. This is because a defective component in the μc-Si:H film is affected by transparent conductive oxide (TCO) texture, as the film thickness of the microcrystalline silicon increases [2]. It has been reported that the defective region consists of vacancies and a low-density amorphous region [2]. We proposed another factor for the formation of a defective region due to the shadowing effect on incident radicals [2], which should reduce the Xc [8]
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