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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.

为了开发一种新的薄膜太阳电池软工艺，研究了从氨性碱性电解液中光辅助电沉积CdTe的方法。用电阻率和霍尔效应测试了电沉积层的电学性能，发现沉积时的多晶层为p型，其电阻率为10^7~10^9Ωcm，载流子密度为10^9~10^&lt；-3，迁移率约为1 cm^2V^&lt；-1&gt；S这种来自碱性镀液的高电阻率可能导致了低效率的太阳能电池。用透射电子显微镜研究了碱性电解液中电沉积层的微观结构，并与传统的酸性硫酸盐电解液中的电沉积层进行了比较。在碱性电解液中沉积的CdTe膜层由晶粒度约为10 nm的无规则取向的微晶组成，而在酸性电解液中沉积的膜层由具有择优生长取向的缺陷柱状晶组成。每个柱状物的直径约为150 nm。在碱性电解液中沉积的多晶CdTe颗粒较小，表明在电沉积过程中经常会有新的颗粒形核。在Ar气氛中573K热处理1h，碱性电解液中的CdTe颗粒长大约4倍，但同时在晶界形成了纳米空洞。相反，在相同的条件下，酸性电解液中的CdTe颗粒不会生长。由于高效率太阳电池需要大尺寸的CdTe薄膜，因此控制电沉积过程中新晶体的形核和通过退火来控制薄膜的晶粒生长是非常重要的。