Raghuwanshi Mohit, Chugh Manjusha, Sozzi Giovanna, Kanevce Ana, Kühne Thomas D, Mirhosseini Hossein, Wuerz Roland, Cojocaru-Mirédin Oana
RWTH Aachen University, Sommerfeldstraße 14, 52074, Aachen, Germany.
Dynamics of Condensed Matter and Center for Sustainable Systems Design, Chair of Theoretical Chemistry, University of Paderborn, 33098, Paderborn, Germany.
Adv Mater. 2022 Sep;34(37):e2203954. doi: 10.1002/adma.202203954. Epub 2022 Aug 17.
Growth of Cu(In,Ga)Se (CIGS) absorbers under Cu-poor conditions gives rise to incorporation of numerous defects into the bulk, whereas the same absorber grown under Cu-rich conditions leads to a stoichiometric bulk with minimum defects. This suggests that CIGS absorbers grown under Cu-rich conditions are more suitable for solar cell applications. However, the CIGS solar cell devices with record efficiencies have all been fabricated under Cu-poor conditions, despite the expectations. Therefore, in the present work, both Cu-poor and Cu-rich CIGS cells are investigated, and the superior properties of the internal interfaces of the Cu-poor CIGS cells, such as the p-n junction and grain boundaries, which always makes them the record-efficiency devices, are shown. More precisely, by employing a correlative microscopy approach, the typical fingerprints for superior properties of internal interfaces necessary for maintaining a lower recombination activity in the cell is discovered. These are a Cu-depleted and Cd-enriched CIGS absorber surface, near the p-n junction, as well as a negative Cu factor (∆β) and high Na content (>1.5 at%) at the grain boundaries. Thus, this work provides key factors governing the device performance (efficiency), which can be considered in the design of next-generation solar cells.
在贫铜条件下生长的铜铟镓硒（CIGS）吸收层会导致大量缺陷掺入体相中，而在富铜条件下生长的相同吸收层则会形成缺陷最少的化学计量体相。这表明在富铜条件下生长的CIGS吸收层更适合用于太阳能电池应用。然而，尽管有预期，但具有创纪录效率的CIGS太阳能电池器件都是在贫铜条件下制造的。因此，在本工作中，对贫铜和富铜的CIGS电池都进行了研究，并展示了贫铜CIGS电池内部界面（如p-n结和晶界）的优异特性，这些特性一直使其成为创纪录效率的器件。更确切地说，通过采用相关显微镜方法，发现了维持电池中较低复合活性所需的内部界面优异特性的典型特征。这些特征包括靠近p-n结处贫铜且富镉的CIGS吸收层表面，以及晶界处负的铜因子（∆β）和高钠含量（>1.5 at%）。因此，这项工作提供了控制器件性能（效率）的关键因素，可在下一代太阳能电池的设计中加以考虑。
