Understanding dimensionality in thin film solar cells

该项目将专注于使用不同维度材料的薄膜和太阳能电池的制造和分析。通过直接比较1D，2D和3D晶格材料，我们将确定它们的结构对载流子传输，缺陷形成和最终太阳能电池性能的作用。承担该项目的学生将在斯蒂芬森可再生能源研究所（SIRE）工作。SIRE已经建立了CdTe，Sb 2Se 3和GeSe的太阳能电池平台，他们将成为使用这些材料的薄膜沉积和太阳能电池制造以及相关结构和器件级分析技术的专家。目前市场领先的薄膜太阳能电池技术碲化镉（CdTe）是一种具有典型3D晶格的材料。因为薄膜具有多晶晶粒结构，这意味着它们总是包含晶界。对于3D晶格材料，由于存在悬挂键，晶界成为高复合的来源，悬挂键需要仔细钝化材料才能发挥作用。这增加了生产过程的额外复杂性和成本，并且即使采用钝化，晶界仍然是有限的。最近的研究重点一直是使用低维材料的可能性，以尽量减少多晶性对太阳能电池性能的影响。硒化锑，Sb 2Se 3，太阳能电池是一个关键的例子，由于它们的一维纳米带晶体结构，其中共价键合的带通过货车der Walls键保持在一起，因此在性能上迅速发展。二维纳米片材料，如硒化锗，GeSe，处于更早期的发展阶段，因此甚至不太了解，但同样显示出作为下一代太阳能电池材料的高度前景。关于低维度在多大程度上有益于薄膜材料仍有许多问题有待回答：取向或条带/片材控制载流子传输的程度如何，它们实际上是否具有减少的电子活性缺陷，晶粒结构起什么作用，太阳能性能可以发挥多远？该项目将专注于使用不同维度材料的薄膜和太阳能电池的制造和分析。通过直接比较1D，2D和3D晶格材料，我们将确定它们的结构对载流子传输，缺陷形成和最终太阳能电池性能的作用。

This project will focus on fabrication and analysis of thin films and solar cells using materials with different dimensionality. By directly comparing 1D, 2D and 3D lattice materials we will determine what role their structure plays on carrier transport, defect formation and ultimately solar cell performance. The student undertaking the project will be based in the Stephenson Institute for Renewable Energy (SIRE). Solar cell platforms for CdTe, Sb2Se3 and GeSe are already established in SIRE and they will become an expert in thin film deposition and solar cell fabrication using these materials, as well as associated structural and device level analysis techniques. The current market-leading thin film solar cell technology cadmium telluride, CdTe, is a material with a typical 3D crystal lattice. Because thin films have a polycrystalline grain structure this means they invariably contain grain boundaries. For 3D lattice materials, grain boundaries become sources of high recombination due to the presence of dangling bonds which need to be carefully passivated for the material to function1. This adds additional complexity and cost to the production process and even with passivation, the grain boundaries remain limiting. Recently research focus has been on the possibility of using lower dimensional materials as a way to minimise the impact of polycrystallinity on solar cell performance. Antimony selenide, Sb2Se3, solar cells are a key example of this having rapidly developed in performance due to their 1D nano-ribbon crystal structure, where covalently bonded ribbons are held together via Van der Walls bonds. 2D nano-sheet materials such as germanium selenide, GeSe, are at an even earlier stage of development and consequentially even less well understood but similarly show a high degree of promise as a next-generation solar cell material. There are still a number of questions on the extent to which the low-dimensionality benefits thin film materials to be answered: How much does orientation or the ribbons/sheets control carrier transport, do they actually have reduced electronically active defects, what role does grain structure play, how far can solar performance be taken?This project will focus on the fabrication and analysis of thin films and solar cells using materials with different dimensionality. By directly comparing 1D, 2D and 3D lattice materials we will determine what role their structure plays on carrier transport, defect formation and ultimately solar cell performance.