基于薄膜硅太阳电池电荷传输特性考虑的减反和陷光研究

薄膜太阳电池中由于光吸收层厚度的减小，高效的减反和陷光对实现高转换效率尤为重要。通常，传统电池内部的绒面陷光结构在提升短路电流密度的同时会导致开路电压和填充因子的下降。针对陷光与电荷传输之间的矛盾，本项目提出电池外部绒面和内部平面结构相结合的研究方案，以实现物理绒面与光学散射的独立调控。首先，利用光伏玻璃进光面的外部绒面和减反膜复合结构将阳光以一定角度耦合进入玻璃衬底，并抑制其反射；然后，再利用玻璃另一侧由透明导电材料与填充材料所组成的平面透射相位光栅将具有高衍射效率的高阶衍射光以更大角度耦合进入光电转换功能层。通过上述外部绒面和内部平面结构的联合配光，可以大幅度降低光在功能层中进入逃逸锥的几率。由于内部无绒面结构，更能显著降低功能层的生长缺陷，以保证高效的光电转换和电荷传输。本项目的实施将为电池减反和陷光研究提供新的思路--基于优化电荷传输特性考虑的光学设计。

High-efficient antireflection and light-trapping are essential for high conversion efficiency of thin-film silicon solar cells due to their reduced thickness of absorption layers. In general, the conventional texturized light-trapping structures inside solar cells do increase the short-circuit current density, accompanied with the decrease of open-circuit voltage and fill factor. To relieve the trade-off between light-trapping and carrier transportation, this project is going to study a novel antireflection and light-trapping structure, composed of exterior textures and interior flattened surfaces, which decouples the physical textures from light scattering. First, the exterior textures with antireflection coatings will couple solar irradiances into solar glass with a certain angle and suppress the reflections. And then, the planar transmission phase gratings, consisting of fillers and transparent conductive oxides, on the other side of solar glass, will couple the higher-order diffracted beams with higher diffraction efficiencies and larger angles into active layers. With the aid of such joint light distribution, the probability of entry into escape cone will be significantly reduced; the defects in active layers will be greatly suppressed due to no texturized structures, compared with the growth of active layers on conventional textures, simultaneously realizing high-efficient light management and carrier transportation. This project will provide a novel way for antireflection and light-trapping, which is an optical design considering the optimal carrier transportation.