Correlative characterization of co-evaporated Cu2ZnSnSe4 thin-films - CORRKEST

近年来，锌黄锡矿结构的Cu_2ZnSn（S，Se）_4化合物半导体材料作为薄膜太阳能电池的吸收材料得到了广泛的研究。对这些化合物的快速增长的兴趣可以归因于构成原材料的低成本和丰富性以及它们有益的光电特性（直接带隙和高吸收系数），这与已建立的黄铜矿的光电特性相似。然而，与带隙相比，锌黄锡矿太阳能电池的主要限制之一是其开路电压的大损失，其中这种现象的原因尚不清楚。锌黄锡矿太阳能电池的电子结构很可能受到第二相的强烈影响。由于锌锡锡石化合物在相图中存在的区域很窄，在制备和加工锌锡锡石薄膜过程中容易形成第二相。然而，还没有建立一个明确的联系之间的第二相的发生和电子结构的锌黄锡矿吸收剂。这是由于二次相的表征极具挑战性。在这个建议的项目中，我们计划进行相关的表征Cu 2 ZnSnSe 4薄膜，共蒸发制备。将应用的分析技术包括原子探针断层扫描、电子显微镜、光致发光和阴极发光以及电气表征。该项目的主要目标是了解锌黄锡矿薄膜的电子结构（带隙，缺陷，复合路径），体成分和微观结构（第二相，有序-无序转变）之间的相关性。通过建立基本的组成-结构-性能关系，我们的目标是开发一种用于气溶胶的材料设计概念，这将支持太阳能电池的知识驱动开发。

Recently, kesterite structured Cu2ZnSn(S,Se)4 compound semiconductors have been intensively investigated as absorber materials for thin-film solar cells. The rapidly growing interest in these compounds can be ascribed to the low cost and abundance of the constituting raw materials as well as their beneficial opto-electronic properties (direct band gap and high absorption coefficients), which are similar to those of the established chalcopyrites. However, one of the main limitations of kesterite solar cells is their large loss in open circuit voltage, compared to the band gap, where the reasons for this phenomenon are unclear. The electronic structure of kesterite solar cells is most likely strongly influenced by secondary phases. Secondary phases can be easily formed during fabrication and processing of kesterite films, as kesterite compounds have very narrow existence regions in phase diagrams. However, a clear link between the occurrence of secondary phases and the electronic structure of kesterite absorbers has not yet been established. This is due to the fact that characterization of secondary phases is highly challenging. In this proposed project, we plan to perform correlative characterization on Cu2ZnSnSe4 films, prepared by co-evaporation. The analytical techniques, which will be applied, will include atom probe tomography, electron microscopy, photo- and cathodoluminescence as well as electrical characterization. The main objective of this project is to understand the correlation between the electronic structure of kesterite thin-films (band gap, defects, recombination paths), the bulk composition and the microstructure (secondary phases, order-disorder transition). By establishing fundamental composition-structure-property relationships, we aim to develop a material design concept for kesterites that will support a knowledge driven development of solar cells.