成果報告書詳細
管理番号20170000000082
タイトル*平成27年度中間年報 高性能・高信頼性太陽光発電の発電コスト低減技術開発 先端複合技術型シリコン太陽電池、高性能CIS太陽電池の技術開発 太陽電池用原料品質の最適化及び結晶欠陥の評価技術の開発・制御
公開日2017/3/31
報告書年度2015 - 2015
委託先名株式会社トクヤマ
プロジェクト番号P15003
部署名新エネルギー部
和文要約
英文要約Title: Development of high performance and reliable PV modules to reduce levelized cost of energy, Technological development of advanced composite silicon solar cells and high-performance CIS solar cells, Development and control of the evaluation technology of optimization and crystal defects of raw material quality for solar cells(FY 2015-2017) FY 2015 Annual Report

For the purpose of quality optimization of polysilicon raw material, it is understand the behavior of impurities and the impact on solar cell conversion efficiency. Since the segregation of carbon and metal impurities takes place in single crystal ingot pulled by the Czochralski method, it is essential to evaluate the full length from the top to the bottom of the ingots.
(1) Effect on cell conversion efficiency of the pulling conditions and the carbon concentration
We investigated the effect of pulling conditions and the carbon concentration of the ingots, using the wafer of high oxygen concentration of the top position of ingot. In the as-sliced wafer, the difference by pulling condition was not observed. However, after boron diffusion of cell process, by the difference of the pulling conditions, the difference in life time was observed. In the carbon concentration in the bulk is low, life time is high, further, and effect of pulling condition was found to be very large. In the thermal condition of cell process, lifetime is reduced by growth of oxygen precipitates. In the ingot top of the high oxygen concentration, a small amount of carbon becomes the nucleus of oxygen precipitation and affects the lifetime. In addition, it was found that the thermal conditions of ingot pulling changes the lifetime after cell process. Yield of good quality wafer can be greatly improved by pulling conditions.
(2) Effect on cell conversion efficiency of metal impurities
Metal impurities concentrations become higher in the bottom side of the ingot by segregation. Using the ingot was pulled from a raw material obtained by adding Fe and Ni, it was subjected to cell experiments. In the as-sliced wafer, the influence of metal contamination was remarkable. On the other hand, after the thermal process, the influence of metal contamination was not observed. The metals of the large diffusion constant, such as Fe and Ni is considered be guttered by phosphorus diffusion of cell process. From the above results, in the high temperature process cell, the impact of growth of oxygen precipitates in a thermal process is larger than the metal impurities. Therefore, elucidating the mechanism of generation and growth of oxygen precipitates by pulling conditions and carbon impurities is a priority issue.
(3) Observation of oxygen precipitates by transmission electron microscopy
Spherical aberration correction electron microscopy was effective to observe the structure, morphology and dislocations of small oxygen precipitates. The following year, observe the oxygen precipitates that grew in thermal condition of cell process in wafer of different pulling conditions and carbon concentrations, and examine the relationship between the cell characteristics and the oxygen precipitates.
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