Collaborative Research: SusChEM: Using Ultrafast Carrier Dynamics to Link Structure, Properties, and Performance in Single-Crystal Cu2ZnSn(S,Se)4 for Thin Film Photovoltaics

合作研究：SusChEM：利用超快载流子动力学将薄膜光伏用单晶 Cu2ZnSn(S,Se)4 的结构、性质和性能联系起来

• 批准号: 1507988
• 负责人: Jason Baxter
• 金额: $ 29.83万
• 依托单位: Drexel University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-01 至 2019-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1507988&HistoricalAwards=false
• 关键词: Collaborative; Research; SusChEM; Using; Ultrafast

Non-technical Description: Copper zinc tin sulfide selenide (CZTSSe) is a promising candidate material for use in solar cells because it strongly absorbs visible light and is composed primarily of earth-abundant, non-toxic elements. However, fundamental scientific understanding of CZTSSe has been limited by difficulties in fabricating thin films of high quality. In this project, researchers at Drexel University and the University of Delaware grow bulk crystals of CZTSSe and characterize their response to light. This approach enables identification of relationships between elemental composition and photovoltaic response, which can lead to both near-term increases in efficiencies and improved estimates of the practical performance limits of solar cells made from this emerging material. Multiple graduate and undergraduate student researchers participate in this project. Additionally, researchers use a mobile solar module to bring concepts in solar energy conversion to K-12 students in the Philadelphia and Newark communities, especially from under-represented groups, through events such as Philly Materials Day.Technical Description: CZTSSe thin films have shown promising photovoltaic efficiencies up to 12.6%, but they are still far below the theoretical limit of over 30%. Photocurrent and photovoltage in CZTSSe solar cells are limited by short (nanoseconds) photoexcited carrier lifetimes. Further improvements in efficiency will require full understanding of how materials composition, intrinsic point defects, and interfaces affect ultrafast photoexcited charge carrier dynamics. However, complex defect chemistry and highly non-equilibrium conditions of thin film growth result in high densities of grain boundaries and secondary phases, posing a significant impediment to fundamental understanding. In this project, the collaborative research team grows high-quality, quasi-equilibrium CZTSSe single crystals and interrogates them using ultrafast spectroscopic probes to understand how carrier dynamics depend on composition, defects, and interfaces in CZTSSe single crystals. This work is expected to lead to new understanding of the relationships between ultrafast carrier dynamics, processing, material and interface properties, and photovoltaic performance. Specifically, the project relies on terahertz spectroscopy and transient reflectance spectroscopy coupled with finite element transport-recombination models to determine photoexcited carrier lifetimes, mobilities, and dominant recombination mechanisms. Lifetimes and mobilities are measured as a function of Cu:Zn:Sn and S:Se ratios and are correlated to device performance. Additionally, studies of surface/interface recombination in CZTSSe-CdS heterojunctions and the effects of grain boundaries in quasi-equilibrium polycrystals enable extrapolation of new fundamental scientific understanding to thin film photovoltaic devices.

非技术描述：铜锌锡硫化物硒化（CZTSSE）是一种有前途的候选材料，可用于太阳能电池，因为它强烈吸收可见光，主要由土壤丰富的无毒元素组成。但是，对CZTSSE的基本科学理解受到制造高质量薄膜的困难的限制。在这个项目中，德雷克塞尔大学和特拉华大学的研究人员种植了CZTSSE的散装晶体，并描述了他们对光线的反应。这种方法可以识别元素组成与光伏反应之间的关系，这可以导致效率的近期提高以及改善对这种新兴材料制造的太阳能电池的实际性能限制的估计。多个毕业生和本科生研究人员参加了该项目。此外，研究人员使用移动太阳能模块将太阳能转化的概念带给了费城和纽瓦克社区的K-12学生，尤其是来自代表性不足的群体，例如Philly Materials Day等事件。技术描述：CZTSSE薄膜已显示出令人鼓舞的光伏效率，但最多可达12.6％，但它们仍在30％以下。 CZTSSE太阳能电池中的光电流和光电压受到短（纳秒）光激发载体寿命的限制。效率的进一步提高将需要充分了解材料组成，固有点缺陷和接口如何影响超快的光激发电荷载体动力学。但是，薄膜生长的复杂缺陷化学和高度非平衡条件会导致高密度的晶界和次级阶段，从而对基本理解产生了重大障碍。在这个项目中，协作研究团队增长了高质量的准平衡CZTSSE单晶，并使用Ultrafast Spectroscopic探针询问它们，以了解载体动力学如何依赖于CZTSSE单晶的组成，缺陷和接口。预计这项工作将导致对超快载体动力学，处理，材料和界面属性以及光伏性能之间的关系的新理解。具体而言，该项目依赖于Terahertz光谱和瞬态反射率光谱，并结合有限元元件传输型结合模型来确定光激发载体寿命，迁移率和主流重组机制。寿命和迁移率是Cu：Zn：SN和S：SE比率的函数，与设备性能相关。此外，对CZTSSE-CD异质结构中的表面/界面重组的研究以及准平衡多晶中晶界的影响，使得可以将新的基本科学理解推断到薄膜光伏设备上。

项目成果

Distinguishing Thermal and Electronic Effects in Ultrafast Optical Spectroscopy Using Oxide Heterostructures

• DOI: 10.1021/acs.jpcc.7b09592
• 发表时间: 2018-01
• 期刊: Journal of Physical Chemistry C
• 影响因子: 3.7
• 作者: S. Smolin;A. Choquette;Jiayi Wang;S. May;J. B. Baxter

A Noble‐Transition Alloy Excels at Hot‐Carrier Generation in the Near Infrared

• DOI: 10.1002/adma.201906478
• 发表时间: 2020-04
• 期刊: Advanced Materials
• 影响因子: 29.4
• 作者: Sara K F Stofela;O. Kizilkaya;B. Diroll;T. R. Leite;Mohammad M. Taheri;Daniel E. Willis;J. B. Baxter;W. Shelton;P. Sprunger;K. McPeak

Measurement of Carrier Dynamics in Photovoltaic CZTSe by Time-Resolved Terahertz Spectroscopy

通过时间分辨太赫兹光谱测量光伏 CZTSe 中的载流子动力学

• 发表时间: 2018
• 期刊: Conference record of the IEEE Photovoltaic Specialists Conference
• 作者: Li, Siming;Lloyd, Michael A.;Golembeski, Andrew A.;McCandless, Brian E.;Baxter, Jason B.
• 通讯作者: Baxter, Jason B.