学术报告201641-Kazuo Nakajima教授学术报告会

发布者:史杨审核:yqk终审:发布时间:2016-11-24浏览次数:2358

 报告题目:Growth of high quality Si ingots for solar cells using the dendritic cast method and the noncontact crucible method

报告时间:1125日(周五)上午10

报告地点:硅材料国家重点实验室一号楼会议室

邀请人:杨德仁教授 

ABSTRACT

The most important subject of the cast method will be the assurance of the high yield of higher efficiency solar cells than 19.0 % for the regular cell structure. We proposed the noncontact crucible (NOC) method to obtain uniform large Si single ingots with sufficient quality to obtain solar cells with a high conversion efficiency and a high yield using a cast furnace. In this method, the Si melt has a large low-temperature region in its upper central part to allow natural crystal growth inside it. Nucleation occurs on the surface of the Si melt using a seed crystal, and an ingot grows inside the Si melt without contact with the crucible wall. A furnace with two zone heaters was developed to design as a simpler furnace for practical use. A single ingot with a maximum diameter ratio of 0.9 and a maximum diameter of 45.0 cm was obtained using a 50 cm diameter crucible. The etch pit density in the centre of these ingots was generally on the order of 102 ‒ 104cm-2 without necking technique.Minority carrier lifetime at the injection level of 1 × 1015/cm3 was 1- 3 ms after P gettering.A p-type ingot was grown after furnace cleaning. The solar cells were prepared using full wafers (15.6 × 15.6 cm2) cut from the ingot by the FREA AIST standard process. Using the same solar cell structure and process to obtain an average conversion efficiency of 19.1% for p-type Czochralski (CZ) wafers, the highest conversion efficiency of 19.14% and the average conversion efficiency of 19.0% were obtained for our wafers. The scattering width was only 0.34% which was quite narrow because of its high uniformity. Using the cast furnace, p-type solar cells with the conversion efficiency and yield as high as those of CZ solar cells were obtained by the NOC method for the first time.