串联式一维核壳结构纳米阵列太阳能电池的设计、制备及光伏性能研究

All solar cells based on a single photoactive material face a dilemma on optical absorption range and obtainable photovoltage. Using a material with narrow band gap can extend optical absorption range and uses a wider part of the solar spectrum, but resulting in a smaller voltage output. While using a wide band gap material can offer a higher voltage output, the current output would be limited by the narrow optical absorption spectrum. To solve this problem, tandem solar cell has been fabricated by vertically stacking two photovoltaic units in series. However, such tandem solar cell typically involves preparation of complicated multilayer of semiconductor thin films via vacuum processes. This project proposes a new type of low-cost tandem solar cell based on 1-D core-shell nanocable arrays. In this design, two photovoltaic units would be connected by the electrolyte between them. Thus, two photovoltaic units can be independently fabricated and optimized to deal with dilemma mentioned. By independently controlling the compositions, morphologies, interface structures of the two coupled core-shell nanocable arrays, two photovoltaic units with complementary optical absorption and matched electrical properties would be prepared and assemble into high performance tandem solar cells. The propose project would provide useful information for the future development of high performance nanocable-based solar cell with new device structures.

太阳能电池存在一矛盾体系，即窄禁带半导体吸光范围广，太阳能电池电流密度较大而开路电压较低；宽禁带半导体吸光范围窄，电池电流密度较小而开路电压较高。串叠太阳能电池采用多层不同能隙半导体组成多个p-n结，可达最佳太阳光吸收效率，显著提高电池转化效率。但是串叠太阳能电池的制造工艺复杂，实验设备成本昂贵。因此，本项目旨在设计和发展制造工艺简单、成本低廉的新型纳米结构串联太阳能电池，采用电解液将两个一维核壳结构纳米阵列组装起来，制备串联式全一维核壳结构纳米阵列太阳能电池，实现太阳全光谱吸收和光电转化，并解决半导体敏化太阳能电池开路电压小及光电转化效率低等问题。构造和制备多种不同的一维核壳结构纳米阵列，系统研究纳米阵列的分布密度、尺寸大小、物相组成、成分含量、晶体质量和界面结构等特征与纳米阵列的能带结构和光学性能以及串联太阳能电池的光伏性能之间的关系，为新型纳米结构太阳能电池的发展提供理论及实验依据。

本项目中，我们针对量子点敏化太阳能电池的光阳极与对电极的设计制备、太阳能电池的光伏性能提高，开展了系统研究，主要内容和结果如下：（1）合成了ZnO纳米线阵列作为电子传输层，通过敏化不同窄带隙半导体材料，制备了不同核壳结构纳米阵列工作电极，达到增强吸收太阳光的目的；通过增大电池的异质结面积促进电子-空穴对的有效分离，缩短少数载流子的扩散路径，提供有效的载流子传输路径，达到提高电池光电转换效率的目的。（2）制备不同纳米结构金属硫属化合物纳米结构，通过提高比表面和导电性来提高对电极材料的催化活性，减少界面转移电阻，提高太阳能电池的光伏性能。（3）系统表征和分析了电池性能参数，包括短路电流密度Jsc、开路电压Voc、填充因子FF、光电转化效率PEC、串联电阻Rs和并联电阻Rsh等，进一步优化电池材料和器件结构，为发展新型纳米结构太阳能电池提供了理论及技术基础。上述研究工作取得多项具有一定创新性和系统性的研究结果，部分研究结果已在Adv. Mater.、Adv. Energy Mater.、Nano Energy、Small、ACS Appl. Mater. Interfaces、J. Mater. Chem. A、和Nanoscale等国际期刊上发表论文25篇，并获授权1项中国发明专利和2项美国发明专利。