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Development of a Soft Process for CdTe Solar Cell using Photo-assisted Electrodeposition

利用光辅助电镀技术开发 CdTe 太阳能电池软工艺

基本信息

批准号：
14350399
负责人：
HIRATO Tetsuji
金额：
$ 9.92万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

To develop a new soft process for CdTe thin layer solar cell, photo-assisted electrodeposition of CdTe from ammoniacal basic electrolytes was investigated. The electrical properties of polycrystalline CdTe layers electrodeposited were examined by resistivity and Hall effect measurement, As-deposited CdTe layers were found to be p-type with resistivity of 10^7-10^9Ω cm, carrier density of 10^9-10^<11> cm^<-3>, and mobility ca. 1 cm^2 V^<-1> s^<-1>. This high resistivity of CdTe layer from basic baths probably leads to low-efficiency solar cells. The microstructures of CdTe layers electrodeposited from basic electrolytes were investigated by transmission electron microscopy and compared with those from a conventional acidic sulfate electrolyte. As^- deposited CdTe layers from a basic electrolyte were composed of randomly oriented crystallites with a grain size of ca.10 nm, while those from an acidic electrolyte consisted of defective columnar grains with a <111> preferred growth orientation. Each of the columnar has a diameter of of ca.150 nm. The small grain size of the polycrystalline CdTe deposits from the basic electrolyte suggests that nucleation of new grains occurs frequently during electrodeposition. By annealing at 573 K for 1 h in an Ar atmosphere, CdTe grains from the basic electrolyte grew by about a factor of four, but at the same time, nano-voids were formed at the grain boundaries. In contrast, CdTe grains from the acidic electrolyte did not grow by annealing the same conditions. Since a large grain size is desirable for CdTe layers to be used in high-efficiency solar cells, it is important to control the nucleation of new grains during electrodeposition and the grain growth of CdTe deposits by annealing.

为了开发 CdTe 薄层太阳能电池的新软工艺，研究了从氨碱性电解质中光辅助电沉积 CdTe。通过电阻率和霍尔效应测量测试了电沉积多晶CdTe层的电学性能，发现沉积态CdTe层为p型，电阻率为10^7-10^9Ω·cm，载流子密度为10^9-10^<11>cm^-3>，迁移率约为100％。 1 厘米^2 V^<-1> s^<-1>。碱性浴中 CdTe 层的这种高电阻率可能会导致太阳能电池效率低下。通过透射电子显微镜研究了碱性电解质电沉积的 CdTe 层的微观结构，并与传统酸性硫酸盐电解质的微观结构进行了比较。来自碱性电解质的As-沉积的CdTe层由晶粒尺寸约为10nm的随机取向的微晶组成，而来自酸性电解质的那些由具有<111>优选生长取向的有缺陷的柱状晶粒组成。每个柱状体的直径约为150nm。来自碱性电解质的多晶 CdTe 沉积物的小晶粒尺寸表明，在电沉积过程中经常发生新晶粒的成核。通过在 Ar 气氛中在 573 K 下退火 1 小时，来自碱性电解质的 CdTe 晶粒生长了约四倍，但同时在晶界处形成了纳米空隙。相比之下，在相同条件下退火时，酸性电解质中的 CdTe 晶粒不会生长。由于大晶粒尺寸对于用于高效太阳能电池的 CdTe 层是理想的，因此在电沉积过程中控制新晶粒的成核以及通过退火控制 CdTe 沉积物的晶粒生长非常重要。