Production Technology of High-Efficiency Amorphous Solar Cells by Radical Control

本研究的目的是发展一种新的工艺技术，以制备高质量的非晶薄膜，用于高效率的太阳能电池。本文介绍了氢自由基化学气相沉积法（Hydrogen RadicalCVD），利用氢自由基对气相反应和表面反应的双重影响，尝试制备了a-Si：H、μ c-Si：H、a-SiC：H和μ c-SiC：H等硅相关薄膜，并对其沉积机理进行了分析，对氢自由基浓度进行了测量。(1)研究发现，通过改变SiH 4或Si 2 H6的浓度，可以控制氢自由基对生长表面的影响，可以制备μ c-Si：H和a-Si：H。获得了高光敏性和光稳定性的低氢含量a-Si：H薄膜。p型和n型薄膜的电学特性也很好。(2)以Si_2H_6和C_2H_2为源气体制备了a-SiC：H薄膜。结果表明，采用微波激发引入乙炔，可以在很宽的范围内控制薄膜的性质，并形成稳定性高的薄膜。通过降低Si_2 H_6的浓度，制备了μ c-Si：H薄膜。(3)采用简化的一维模型，对氢自由基CVD沉积机理进行了计算机模拟分析。结果，据估计，有助于膜沉积的自由基物种通过改变源气体浓度而有效地变化。(4)通过由电阻测量检测氢自由基与之碰撞的铂丝中的温度变化来评估氢自由基密度，并且弄清其对产生条件的依赖性及其在CVD室中的分布。

The purpose of this study is to develop a new process technology to prepare high-quality amorphous thin films for high-efficiency solar cells. We have introduced hydrogen-radical CVD in which hydrogen radicals may affect both gas phase reaction and surface reaction and tried to prepare silicon related films such as a-Si : H,mu c-Si : H,a-SiC : H and mu c-SiC : H.Moreover, analysis of deposition mechanism and measurements of hydrogen radical density was carried out.(1) It was found that, by changing the concentration of SiH4 or Si2H6, the effect of hydrogen radicals on growth surface can be controlled and mu c-Si : H as well as a-Si : H can be prepared. Low hydrogen content a-Si : H films with high photosensitivity and high stability under light illumination were obtained. Electrical characteristics in p-type and n-type films also was good.(2) a-SiC : H films were prepared by using source gases of Si2H6 and C2H2. It was found that by introducing C2H2 with microwave excitation film properties can be controlled in a wide range and films with high stability can be formed. By decreasing the concentration of Si2H6, mu c-Si : H films were produced.(3) Deposition mechanism in hydrogen-radical CVD was analyzed by computer simulation with a simplified one-dimensional model. As a result, it was estimated that radical species contributing to film deposition is effectively varied by changing source gas concentration.(4) Hydrogen radical density was evaluated by detecting a temperature change in a platinum wire with which hydrogen radicals collide from measurements of electric resistance, and its dependences on generation conditions and its distribution in a CVD chamber was clarified.