氮化镓/硅多界面纳米异质结新型太阳能电池研究

The contradiction existed between the energy dispersivity of sunlight photons and the uniqueness and definiteness of the bandgap energy, as well as that between the site distribution of sunlight absorption and the site location of the collection electrode for a photovoltaic cell, are the two fundamental limitations for the further promotion of its energy conversion efficiency. Aimed directly at solving the two contradictions, we planned to prepare a novel solar cell based on GaN/Si multi-interface nanoheterojunction, which will be accomplished by growing GaN nanostructures on silicon nanoporous pillar array (Si-NPA), a unique silicon hierarchical structure prepared by a hydrothermal method. Here the efficiency for the utilization of the whole sunlight spectrum to produce photon-generated carriers will be greatly promoted through both introducing semiconductors with different bandgap energies and exploiting the size dependence of energy bandgaps for semiconductor nanocrystallites; while the recombination probability for photon-generated carriers during their transport from generating sites to colleting electrode will be largely reduced through shortening the transport length by constructing a complex multi-interface nanoheterojunction. Clearly, both of the two measures will be helpful for promoting the final cell efficiency. Based on controlling the structure and component at the interface and analyzing the photovoltaic properties of the solar cell, the process and physical mechanism relating to the generation, separation, transport and collection of the photon-generated carriers will deeply and systematically studied, and the space configuration and physical model of the multi-interface nanoheterojunction will be built up, accompanied with the clarification on the characteristic parameters for describing the nanoheterojunction. Through evaluating the comprehensive device performance, the study will lay a strong physical and technical foundation for preparing high-efficiency solar cells.

太阳光子能量的分散性与半导体带隙能的唯一性、光子吸收位的分布性与载流子收集电极的局域性，构成了制约传统太阳能电池效率提高的两个根本因素。本项目拟以具有独特层次结构的硅纳米孔柱阵列（Si-NPA）为衬底，通过沉积GaN纳米结构，制备出一种GaN/Si-NPA多界面纳米异质结新型太阳能电池。利用异质结中两种半导体材料带隙差和半导体纳米晶带隙的尺寸依赖性，实现对太阳光全波段的量子吸收，提高光生载流子产生效率；通过构造复杂多界面异质结构，缩短载流子向收集电极传输过程的路径，减小载流子传输过程中的复合几率，最终获得具有较高能量转换效率的太阳能电池。项目还拟通过对电池复杂界面结构及成分的调控和对电池光伏特性的测试与分析，探索纳米多界面异质结中光生载流子产生、分离、输运和收集的物理过程和规律，建立其清晰的空间结构和物理模型，为未来新型高效太阳能电池研制奠定基础。

太阳光子能量的分散性与半导体带隙能的唯一性、光子吸收位置的分布性与载流子收集电极的局域性，构成了制约传统太阳能电池效率提高的两个根本因素。本项目以具有独特层次结构的硅纳米孔柱阵列（Si-NPA）为衬底，通过沉积GaN纳米结构，制备出一种GaN/Si-NPA多界面纳米异质结。为提高GaN/Si-NPA的界面质量并减少缺陷种类和缺陷浓度，探索发展了Si-NPA的氮钝化技术，GaN在Si-NPA上的无催化剂生长技术和ZnO纳米晶诱导生长技术，研究了在制备过程中氨气流量对GaN结构形貌、缺陷种类和相对浓度及的调制规律。在此基础上，制备了基于GaN/Si-NPA的太阳能电池并对其制备条件进行了优化，实现了开路电压0.82 V、短路电流23.21 mA/cm2、填充因子38.5%和电池能量转换效率7.29%的优异性能。通过对电池复杂界面结构及成分的分析并结合电池光伏特性的测试结果，初步澄清了多界面纳米异质结中光生载流子产生、分离、输运和收集的物理过程和规律，建立了多界面纳米异质结电池清晰的空间结构和物理模型，为未来新型高效太阳能电池研制奠定了基础。