高效硅氧纳米复合薄膜/晶体硅异质结太阳电池界面量子输运机理研究与制备

Extensive attention has been paid by scholars both at home and abroad to the silicon heterojunction (SHJ) device since it holds the current efficiency record for silicon-based single junction photovoltaics, which is one of the main candidates for the next industrial standard for high-performance silicon solar cells. While amorphous silicon has been widely accepted as the emitter, back-surface field and buffer materials in the SHJ solar cell, its parasitic light absorption losses and the narrow process window for the preparation are hardly overcome, which renders the development of the a-Si:H/c-Si heterojunction solar cell. In the present project, we will carry out the study of the nanocrystalline hydrogenated silicon oxide (nc-SiOx:H) instead of the amorphous silicon in the SHJ solar cell. Multiscale methods are present to understand the fundamental mechanisms of charge carrier transport and recombination at the heterointerface, such as the ab initio molecular dynamics simulations, hybrid density functional theory, and non-equilibrium Green's equation. The detailed studies include analyzing the modulation of the optical and electronic properties by adjusting the geometric configurations at the heterointerface and oxygen content of the nc-SiOx:H, as well as exploring the effect of the passivating contact layers. Furthermore, we will fabricate high-performance samples of nc-SiOx:H /c-Si SHJ solar cell with intrinsic a-SiOx:H thin layer by employing plasma enhanced chemical vapor deposition (PECVD), physical vapor deposition (PVD) and screen printing techniques. The device parameters of these samples, such as short circuit current, open circuit voltage and fill factor, will also be verified by using the measurement of the solar simulator. It is believed that the present project can provide the new theoretical basis and technical support to improve the performance of nc-SiOx:H /c-Si heterojunction solar cells.

硅异质结太阳电池具有目前单结太阳电池最高的光电转换效率，有潜力成为未来高效太阳电池的工业标准之一。然而由于非晶硅材料具有不可克服的寄生光吸收效应和制备工艺窗口较窄等弊端，制约了其性能的进一步提高。本项目围绕一种新型的高透光率和高导电性的硅氧纳米复合薄膜展开研究，结合第一性原理分子动力学、杂化密度泛函理论和非平衡格林函数法研究载流子在硅氧纳米复合薄膜/晶体硅界面的输运和复合机制，探索氧浓度变化对其光学和电学性质的敏感调控性能，阐明本征非晶薄膜层的钝化机理和工艺参数对钝化性能的调节规律，为实验提供新的理论依据和技术支持。采用等离子体增强化学气相沉积技术、磁控溅射技术和丝网印刷技术制备出高质量的带本征层钝化的硅氧纳米复合薄膜/晶体硅异质结太阳电池样品，测试器件的短路电流、开路电压和填充因子等参数，有望在该新型硅基异质结太阳电池中获得高效光电转化效率并扩大工艺窗口。

硅异质结太阳能电池具有最高的光电转换效率，是未来高效太阳能电池的行业标准之一。然而，非晶硅材料显著的寄生光吸收效应和狭窄的制备窗口限制了进一步的工业应用。本项目主要研究一种高透光率和高导电率的新型硅氧纳米复合薄膜，结合第一原理分子动力学、杂化密度函数理论和非平衡格林函数法，系统研究了非晶硅氧纳米复合膜/晶硅界面载流子的输运机理，探索了通过调整界面氧浓度对其光学和电学性能的敏感调控，阐明了非晶膜层的钝化机理和工艺参数对钝化性能的调控。.主要研究成果如下。(1)系统设计了基于nc-SiOx:H/c-Si异质结太阳能电池的器件结构，采用湿化学法、化学气相沉积等技术制备了高质量的太阳能电池样品。阐明了钝化效应、氧离子空位溶度、钝化层厚度对局部电子态密度和载流子穿透概率的影响，并指出原子级硅原子链的形成是产生pin-hole隧穿效应的物理基础（发表SCI论文1篇）。（2）阐明了一类三元半导体的氧离子输运性质，并给出了其氧离子扩散与衬底匹配度的线性律，提出了该类三元半导体中氧离子高速通道模型并被实验证实，表明了钝化层与衬底的匹配度是影响氧离子输运的一个重要因素（发表SCI论文1篇）。（3）发展了基于第一性原理的量子输运理论，探索空间电荷层的形成过程及其对载流子输运和复合性能的影响规律，评估二维材料界面处的载流子输运性质，并研究了其它具有高透光率和高导电率的可替代钝化层材料（发表SCI论文4篇）。(4)发展了一种新的电极接触工艺，采用等离子体去除金属氧化物表面氧化层的实验方案，从而大大改善器件电极接触的导通性，可提高三倍的载流子迁移率（发表SCI论文1篇）。该方案已得到实验验证（发表SCI论文1篇）。该项目为硅异质结太阳能电池的应用提供了理论基础和技术支持，是未来高效太阳能电池的发展方向。