基于高、低功函数材料的电荷选择性钝化接触及其构建的背结DASH太阳电池

针对高效率单晶硅电池最新发展趋势，本项目提出高低功函数载流子选择性接触层的设计、实现及背结DASH电池研究。具体内容包括：MoOx单层及MoOx/Ag NWs/MoOx多层空穴选择性接触的设计与实现；共掺杂技术对ZnO基电子选择性接触层电导、带隙和功函数的调控；ZnO与c-Si构成的微/纳米复合陷光结构设计与实现；高质量致密超薄SiOx钝化层研究及其对改善器件稳定性的作用；基于MoOx和ZnO构建的DASH电池界面优化和效率提高。创新性在于：提出一种背结DASH电池结构，使得空穴选择性接触的设计和调控更加灵活，器件稳定性更高；提出一种由ZnO与c-Si构成的、有望获得宽谱域超低反射效果的微/纳米复合陷光结构；提出适用于DASH电池的宽带隙、高电导、低功函数ZnO电子传输层的Li、Mg等元素共掺杂技术。通过上述研究，背结DASH电池效率达到23%。本研究也可为其它光电器件研究提供借鉴。

According to the latest advances and future trends of high-efficiency c-Si solar cells the current proposal will firstly focus on back-junction silicon heterojunction solar cells based on carrier selective passivation contacts with high/low work function materials. Detailed research contents include the following aspects. (1) Design and fabrication of MoOx single- and MoOx/Ag NWs/MoOx multi-layered hole-selective contacts with high work functions and high conductivities. (2) Design and fabrication of ZnO electron-selective contacts with wide bandgaps, high conductivities and low work functions by co-doping technique with Li, Mg or other possible elements. (3) Hybrid nano/micro light trapping structures by combining ZnO with tens of nanometer textures and c-Si with micro-scale pyramid surfaces. (4) Ozone oxidation, nitric acid oxidation and plasma oxidation methods for fabrication of high-quality silicon oxide ultra-thin passivation layers and stability improvement of DASH solar cells. (5) Interface optimization of Back DASH c-Si solar cells with MoOx-based hole-selective contacts and ZnO-based electron-selective contacts. .The innovations of this proposal include the following three issues. (1) We propose a back-junction Dopant-free asymmetric heterocontacts (Back DASH) device structure, of which the ZnO/c-Si junction acts as the light incident side and the MoOx/c-Si junction will be placed at the back side. Using this device structure the optical and electrical properties of MoOx hole-selective contacts can be partially decoupled. Much more attentions can be focused on adjustment of work function, bandgap and conductivity with purpose to get high enough band bending near the surface of c-Si wafer at MoOx/c-Si interface. No TCO is necessary on the MoOx which can avoid the possible MoOx degradation caused during the TCO deposition. (2) Another innovation will be the nano/mico-textured light trapping structures formed by micro-structured pyramid texturization of c-Si wafer surface and nano-textured ZnO, which will probably result in an ultra-low reflectivity in a much wide wavelength range. (3) Co-doping technique by Li, Mg or other possible elements is proposed to realize ZnO electron-selective contacts with wide bandgaps, high conductivities and low work functions..The triumph of this proposal will provide optimized device designs and low-cost, high-efficiency technical schemes for the Back DASH solar cells with target conversion efficiency of 23%. Scientific results and technical methods developed in this project also can be applied in other optoelectronic devices such as detectors and LEDs.