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

本研究的目的是开发一种制备高效太阳能电池用高质量非晶薄膜的新工艺。介绍了氢自由基对气相反应和表面反应均有影响的氢自由基CVD方法，并尝试制备了a-Si: H、c-Si: H、a-SiC: H和c-SiC: H等硅相关薄膜，并对沉积机理进行了分析和氢自由基密度测量。(1)发现通过改变SiH4或Si2H6的浓度，可以控制氢自由基对生长表面的影响，可以制备出μ c-Si: H和a-Si: H。制备了氢含量低、光敏性高、光照稳定性好的a-Si: H薄膜。p型和n型薄膜的电特性也很好。(2)以Si2H6和C2H2为源气体制备了a-SiC: H薄膜。结果表明，通过微波激发引入C2H2，可以在较大范围内控制膜的性能，形成高稳定性的膜。通过降低Si2H6的浓度，制备了μ c-Si: H薄膜。(3)采用简化的一维模型，通过计算机模拟分析了氢自由基CVD沉积机理。结果表明，气体浓度的变化有效地改变了促进膜沉积的自由基种类。(4)通过测量电阻测量氢自由基与铂丝发生碰撞时的温度变化来评估氢自由基密度，并阐明了氢自由基密度与生成条件的关系及其在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.