金属微腔效应提高聚合物并联太阳能电池效率的研究

Highly efficient polymer solar cells have attracted more and more investigations.Currently, the narrow absorption spectrum of the polymer materials is the major restriction to obtain higher power conversion efficiency of the polymer solar cells. This phenomenon is attributed to a low utilization of photons. In order to settle this problem, we induce a new structure of parallel polymer solar cells that with an absorption spectrum cover the whole visible range, which is FTO/TiO2/PCDTBT: PCBM/WO3/Ag/WO3/P3HT:ICBA/TiO2/Al. According to the complementary absorption spectrum of the two active layer materials, changing the parameter of layers properly can improve the photos utilization. By adjusting the thicknesses of Ag electrode and WO3 hole transport layer of the bottom solar cell, the transmission of light, which wavelength is below 600nm,can be inhanced strongly. In the top solar cell, the two electrodes constitute a metal macrocavity structure. Such transmission light makes round trips between the two metal mirrors until the light waves became a multiple reflections between the metal mirrors, a stable standing wave formed. This optical resonance would lead to the maximum light absorption in the active layer, increase the utilization of photos and make a larger absorption coefficient. By using the theory investigation of microcavity effect as the direction, we would investigate the simulation of the internal light field distribution, the fabrication of microcavity structure, the optimization of light transmission of the intermediate layer and the voltage balance between the bottom and top solar cells systematically with theory and practice study. Test under the 100mW/cm2 simulated AM1.5G, a higher power conversion efficiency exceed 8% could be obtained.

高效率聚合物太阳能电池是目前研究热点之一。目前限制效率提高的主要原因是单一的聚合物材料吸收光谱窄，对光子利用率不高。为了解决这些问题，我们制作了结构为FTO/TiO2/PCDTBT:PCBM/WO3/Ag/WO3/P3HT:ICBA/TiO2/Al的全可见光谱的并联太阳能电池。根据两种有源层材料的吸收范围对器件分割，底部半透明电池通过调整Ag和WO3的厚度增强600以下光的透射；顶电池中的Ag和Al组成的金属微腔在满足共振条件时，光学共振效应会增强腔内的光电场，提高有源层对入射光的吸收。我们以微腔效应理论研究为指导，从构建微腔结构、模拟器件内部光电场分布、提高中间连接层的光透过率以及保持底顶两个电池电压平衡等方面对并联电池进行系统的理论与实验研究。在强度为100mW/cm2的AM1.5G标准太阳光照下，电池的能量转化效率大于8%。

聚合物太阳能电池具有低成本，重量轻，柔性和可大面积制作等优点，被认为是传统化石能源最佳替代者。但是，聚合物存在的能带间隙大，无法覆盖整个可见光波段导致效率低等固有缺点，导致聚合物太阳能电池始终无法广泛利用。为了解决以上问题，本项目中我们制作了可见光谱全部覆盖的并联结构聚合物太阳能电池。器件结构中根据两种有源层材料的吸收范围对器件设计，底部半透明电池调整电极和电极修饰层增强短波段的透射，使得更多的光经过底电池入射到顶部电池。在顶电池的设计中，我们采用两种金属电极构建微腔结构，通过调整电极厚度、电极之间距离和有源层厚度设计微腔共振条件，利用光学共振效应提高器件内部的光场分布，进而提高整体器件的效率。在项目执行期间，对微腔结构并联光伏电池的工作原理进行了深入的探索，形成了一套光学电学角度提高光伏电池效率的技术方法。发表SCI论文78篇，申请国家发明专利5项。