微观尺度下柔性CZTSSe太阳电池缺陷与载流子输运的特性研究

Bad performance and bending reliability are the main problems that impede the further development and application of flexible CZTSSe solar cells. At present, the internal key factors affecting these two problems are urgently needed to be studied. This project tries to reveal the mechanism of alkaline doping and stress on the microscale defect and carrier transport properties of flexible CZTSSe solar cells. The key idea of this project is to set up relationship between the potential and conductivity distributions and the main defect and energy band of the thin films by using scanning probe technology. At first, the correspondence between alkaline elements and main defect is studied by doping thin films with different main defects. Based on this, the mechanism of alkaline doping on defects in CZTSSe thin films could be revealed. Then the effects of alkaline doping on carrier transport and energy band model are studied by analyzing the potential and conductivity distribution of the thin films. Finally, the micro-mechanism of stress on the performance of flexible solar cells is explored by observing the defects and photon-generated carrier transport behavior under bending condition. Some measures to suppress the performance degradation caused by bending stress are also put forward. This project furthers the research about doping and stress study in flexible CZTSSe solar cells and provides theoretical guide to prepare high-performance and reliable flexible CZTSSe thin film solar cells.

效率低、弯曲稳定性差是阻碍柔性CZTSSe太阳电池进一步发展与应用的主要问题，且目前对于影响这两问题的内部关键因素缺乏决定性研究。本项目拟基于扫描探针技术，揭示微观尺度下碱金属掺杂与应力对柔性CZTSSe太阳电池内缺陷与载流子输运的作用机制，其核心思想是建立电势、电导分布与薄膜内部主要缺陷和能带间的关联。首先，本项目通过对主要缺陷类型不同的薄膜进行掺杂，探索碱金属掺杂元素与各缺陷间的对应关系，揭示碱金属掺杂对薄膜缺陷的作用机制；其次，利用载流子与电势场和导电性间的相关性，研究碱金属掺杂对CZTSSe薄膜载流子输运与能带模型的影响规律；最后，通过实现应力加载条件下缺陷与载流子行为的观测，明确应力导致柔性电池性能下降的微观机制，并探索提升电池弯曲稳定性的措施。本项目是对柔性CZTSSe太阳电池掺杂与应力研究的进一步深化，为制备高效稳定的柔性CZTSSe薄膜太阳电池提供理论指导。

效率低、弯曲后效率衰减是柔性Cu2ZnSn(S,Se)4（CZTSSe）薄膜太阳电池面临的两大问题，且内部微观因素一直未得到系统性的研究。本项目提出将碱金属元素掺杂进CZTSSe薄膜内部，并基于扫描探针技术，研究不同碱金属和弯曲应力对于CZTSSe薄膜缺陷和载流子的影响。具体研究内容总结如下：①在硒化过程中引入气相碱金属元素实现CZTSSe薄膜内碱金属元素的掺杂，研究不同碱金属元素对于薄膜性能的影响，获得较好结晶性和光电性能的掺杂CZTSSe薄膜。②通过分析不同碱金属掺杂的CZTSSe薄膜表面电势和导电性，揭示碱金属对缺陷和载流子的影响规律，明确了晶界成为主要载流子输运通道是获得高效电池的关键因素。③在上述研究的基础上，通过分析弯曲前后CZTSSe薄膜表面电学性能的变化，发现应力造成的晶界处载流子输运困难和材料带隙波动是效率衰减的主要微观因素。构建以掺Al的ZnO纳米线结构作为窗口层的柔性CZTSSe薄膜太阳电池，结果表明其弯曲稳定性强。以上研究内容为发展高效柔性薄膜太阳电池奠定基础。