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

本研究的目的是开发一种新的工艺技术来制备用于高效太阳能电池的高质量非晶薄膜。我们引入了氢自由基能同时影响气相反应和表面反应的氢自由基化学气相沉积，尝试制备了a-Si：H、Mu c-Si：H、a-SiC：H和Mu c-SiC：H等与硅有关的薄膜，并对沉积机理和氢自由基密度进行了分析和测量。(1)通过改变SiH_4或Si2H_6的浓度，可以控制氢自由基对生长表面的影响，制备出Mu-C-Si：H和a-Si：H。获得了低氢含量、高光敏性和高光稳定性的a-Si：H薄膜。P型和n型薄膜的电学性能也较好。(2)以Si2H6和C2H2为源气体制备了a-SiC：H薄膜。研究发现，在微波激励下引入C2H2可以在很大范围内控制薄膜的性能，并可以形成高稳定性的薄膜。通过降低Si2H6的浓度，得到了多层的多晶硅薄膜。(3)采用简化的一维模型对氢自由基化学气相沉积沉积机理进行了计算机模拟分析。结果表明，通过改变源气体浓度，可以有效地改变导致薄膜沉积的自由基种类。(4)通过测量电阻测量，通过检测氢自由基在铂丝中的温度变化来估算氢自由基密度，并阐明了氢自由基密度与产生条件的关系以及它在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.