新型微纳结构硅基柔性太阳能电池研究

This subject starts from design optimization of surface and interfaces in micro-nano structures, utilizing silicon and carbon nanotubes to construct novel composite micro-nano structure with silicon/carbon radial heterojunction, which will enhance optical absorption and carrier collection efficiencies, and achieving the high efficiency in solar cells. Furthermore, its flexible application will also be developed. Based on the analysis of power conversion mechanism, the device physical model will be built to explore the process of charge separation, recombination and their mechanisms at the silicon/carbon interface; meanwhile, the influence of silicon micro-nano structure feature, silicon/carbon interfacial contact property and the charge transfer process on the photovoltaic characteristic will also be investigated. By improving the fabrication method and the passivation process of silicon micro-nano structures, the charge loss induced by surface recombination will be reduced. Furthermore, the graphene/polymer composite thin film is employed as the electrode material to improve the contact between silicon micro-nano structure and the electrode. Through further optimizations in the material properties and device structures, a power conversion efficiency of beyond 12% will be achieved. By incorporating the thin potential flexible property of silicon micro-nano structure and on the basis of the self-developed silicon thinning technology and the transfer technology of silicon nanowire arrays, the solar cells with certain mechanical flexibility will be fabricated and studied. This subject provides further insights in the surface/interface properties and the photoelectric conversion mechanisms in the novel structured solar cells, which will promotes the development and application of new photoelectric conversion materials and devices; at the same time, the study in flexible property will expand the application field of silicon-based solar cells.

本项目从微纳结构表面界面优化设计出发，利用硅材料及碳纳米管构建具有硅/碳径向异质结的新型复合微纳结构，实现光吸收增强及载流子收集效率提高，获得高效太阳能电池，并开发其柔性应用。基于光电转换机理分析，建立器件物理模型，探索硅/碳径向异质结界面载流子分离、复合过程及机理，研究硅结构特征、硅/碳界面接触及电荷传输对光电转换特性的影响规律。通过硅微纳结构设计及表面钝化，减少硅表面引起的电荷复合损失。利用石墨烯/聚合物复合薄膜作为透明上电极，增强硅微纳结构与电极的接触。结合材料性能及器件结构的进一步优化，获得转换效率高于12%的光伏器件。以自主开发的硅减薄工艺与硅纳米线阵列转移技术为基础，结合微纳结构的潜在柔性优势，开发具有一定机械柔性的硅太阳能电池。本项目对新型微纳结构电池中光电转换机理与表面界面的研究，可促进新概念光电转换材料和器件的开发和应用，并拓展硅基太阳能电池的应用领域。

在本项课题中，我们设计并制备了新型硅基微纳结构，并对其陷光机制进行了深入的研究；开发了新型微纳结构太阳能电池，获得了高效硅基柔性太阳能电池器件。首先，开展了硅微纳结构的理论计算和设计工作，对硅纳米结构的陷光机制进行了理论研究，基于理论计算得到了硅纳米结构的陷光和光吸收特性的变化规律。设计了Ag帽子覆盖的新型金属颗粒/硅纳米线复合结构，实现了宽光谱吸收，其陷光效率高于纯硅线34%。这一复合结构对光的吸收表现出显著的径向定域分布的特性，适合于径向结太阳能电池的应用。设计了氧化硅/硅纳米线结构，有效地减少了硅纳米线本征吸收损失。深入开展了贵金属粒子催化辅助刻蚀机理研究，探明了各种工艺条件对硅微纳结构形貌刻蚀的影响。其次，深入研究了硅微纳结构的刻蚀机理。采用碱溶液刻蚀方法制备了金字塔型硅微纳结构，通过贵金属辅助催化刻蚀方法获得了大面积均匀柱形硅纳米线和锥形硅纳米线阵列，实现了全光谱范围平均反射率在1-2%的高效陷光。再次，探究了化学气相沉积法制备石墨烯的生长机理。应用密度泛函理论研究了石墨烯生长过程中碳原子在铜箔上的成核过程。通过改善石墨烯的制备工艺，获得了毫米级单晶石墨烯。最后，我们设计制备了新型硅微纳结构太阳能电池，并对其增效机制进行了深入的研究。设计了Si/SiNW/PEDOT:PSS结构的微纳结构太阳能电池，探索了其光生载流子的产生、界面电荷分离和复合过程及机理，并研究了硅纳米线、PEDOT:PSS的结构性能对太阳能电池光电转换特性的影响。研究了硅表面钝化和微纳结构界面填充机制，实现了微纳结构太阳能电池的增效。基于超薄单晶硅片和新型硅基微纳结构的制备工艺，制备了新型硅基微纳结构柔性太阳能电池。本课题所设计和制备的新型微纳结构和柔性太阳能电池器件拓展了硅基太阳能电池研究领域，促进了新型硅基太阳能电池结构的开发和利用。