基于(Ni,Mg)Ox背场缓冲层的CdTe太阳电池稳定背接触的界面调控及性能研究

Cadmium telluride (CdTe) based thin-film solar cells are regarded as one of the most competitive low-cost photovoltaic technologies. The fabrication of a stable back contact with low contact-resistance represents a major challenge yet extremely important for realizing high performance CdTe solar cells. Currently, the mostly used back contacts containing Cu element are prone to diffuse into the active layer, posing the major limitation on the long-term stability of the devices. In this proposal, we aim to explore a more stable back contact based on the metal oxide (Ni, Mg)Ox, which is a wide bandgap semiconductor with high work function, for the construction of stable and high efficiency CdTe solar cells. To realize well-aligned energetic properties of the back interface of CdTe/(Ni,Mg)Ox/Metal, we start with the modification of the energetic and electrical properties of (Ni,Mg)Ox buffer layer, in combination with surface composition engineering and a back contact annealing step. The surface and interface structures will be studied by various techniques, e.g., synchrotron radiation. The mechanism how the interface regulation influences the back contact structure and properties, and further, how the back contact structure influences the device performance will be systematically investigated. Finally, with a dedicated optimization on the fabrication technology of the (Ni, Mg)Ox back contact, highly stable CdTe solar cells with efficiency more than 17% are expected to be realized.

碲化镉（CdTe）薄膜太阳电池是最具竞争力的低成本太阳电池之一。获得稳定低阻的背接触是CdTe太阳电池制备过程中的难点和关键环节。传统含Cu背接触中的Cu元素容易扩散，严重影响电池的长期稳定性。本项目旨在利用p型高功函宽禁带金属氧化物(Ni,Mg)Ox制备具有背场作用的背接触结构，提高CdTe太阳电池的转换效率和稳定性。针对影响背接触电学性质和稳定性的界面问题，我们首先从(Ni,Mg)Ox缓冲层能带和电学性质调控出发，结合CdTe表面高阻层化学组分调控和背接触激活热处理等手段，实现CdTe/(Ni,Mg)Ox/Metal界面特性调控与匹配。进而采用同步辐射等界面表征手段，研究背接触调控方式对界面匹配的影响规律，以及背接触结构匹配对器件性能的作用机制，阐明影响背接触载流子输运和器件性能的关键机理问题。最后，通过进一步优化背接触制备工艺，开发出效率大于17%且具有高稳定性的CdTe太阳电池。

本项目围绕高稳定CdTe薄膜太阳电池背接触及高效率电池制备，按计划开展研究工作，调控(Ni,Mg)Ox的Mg/Ni比和Ni3+缺陷，有效改善背场缓冲层光学和电学性质；调控(Ni,Mg)Ox背场缓冲层能带结构和快速热处理，促进背接触界面能带匹配和缺陷钝化；基于背接触激活热处理过程，阐明器件性能改善机制。掌握了高稳定高功函背场背接触制备技术，实现了背接触界面匹配调控和精确测量，解决了异质界面缺陷钝化的难点问题，获得了高效率宽光谱CdTe太阳电池结构和制备技术。. 项目实施期间：1）器件层面：制备得到基于(Ni,Mg)Ox背场背接触结构的转换效率达到17.36%的高稳定CdTe薄膜太阳电池，超额完成项目目标；成功制备认证转换效率超过20%的宽光谱响应CdTe太阳电池，该转换效率处于国内领先、国际先进水平；2）发表学术论文10篇，其中以第一/通讯作者发表领域内高水平研究论文6篇；3）以第一发明人申请发明专利5项，授权3项；4）受邀在国内/国际会议做邀请报告4次；5）获得科研奖励1项：“暨南双百英才-暨南杰青”；6）培养硕士研究生6名。