Collaborative Research: Ultrafast Carrier Dynamics in Semiconductor Nanocrystal Solar Cells

合作研究：半导体纳米晶体太阳能电池中的超快载流子动力学

• 批准号: 1333649
• 负责人: Jason Baxter
• 金额: $ 21.48万
• 依托单位: Drexel University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1333649&HistoricalAwards=false
• 关键词: Collaborative; Research; Ultrafast; Carrier; Dynamics

PI: Baxter, Jason / Murray, ChristopherProposal Number: 1333649 / 1335821Institution: Drexel University / University of PennsylvaniaTitle: Collaborative Research: Ultrafast Carrier Dynamics in Semiconductor Nanocrystal Solar CellsClose-packed arrays of semiconductor nanocrystals (NCs), or quantum dots, are ideal systems for fundamental investigations of photo-induced charge and energy transfer in interacting quantum-confined materials. The materials, diameters, and arrangement of the NCs can be used to tune the inter-NC coupling to exploit both the properties of the individual NCs and the long-range effects of the solid. The emergent optical, electronic, and thermal properties of NC superlattices may lead to transformational improvements in applications including photovoltaics, photonics, and thermoelectrics.The broad objectives of this proposal are (1) to understand ultrafast charge carrier generation, separation, recombination, and transport phenomena in semiconductor nanocrystal superlattices, and (2) to control these fundamental photophysical processes to improve solar cell performance. Specifically, we will investigate films of CdSe, CdTe, and Cu2ZnSnS4 (CZTS) NCs. CdSe and CdTe NCs are excellent model systems because their synthesis and optical properties are well-understood, enabling fundamental ultrafast studies of carrier dynamics in glassy arrays and ordered superlattices of a single monodisperse NC species, as well as binary NC superlattices. CZTS NCs provide an exciting new direction for high efficiency photovoltaics made from non-toxic, earth-abundant elements. The PIs will refine the synthesis of monodisperse CZTS NCs to enable meaningful ultrafast spectroscopic characterization.This approach centers on time-resolved terahertz spectroscopy (TRTS) and femtosecond visible/infrared transient absorption (TA) to probe intraband and interband transitions, respectively. THz spectroscopy is an ideal, non-contact probe of electronic materials because the THz frequency regime (0.1 - 3 THz) brackets typical carrier scattering rates in semiconductors. THz spectroscopy is unique in its abilities to distinguish between excitons and free carriers and to measure their dynamics on sub-picosecond to nanosecond time scales, providing an excellent complement to our steady-state field effect transistor (FET) measurements. Pump-probe TRTS and TA are ideal techniques to investigate the dynamics of interfacial charge transfer, recombination, and inter-NC transport of photoexcited carriers on their natural time and energy scales.This work will advance our understanding of the physical phenomena that govern ultrafast exciton and free carrier dynamics in NCs and NC superlattices. Specific studies will include: (1) Determining mechanisms of charge transport in NC superlattices, e.g. by extended states or by activated hopping; (2) Measuring dynamics of inter-NC coupling, interfacial charge transfer, and long-range charge transport in superlattices of a single monodisperse NC species; (3) Determining the dependence of dynamics and transport mechanisms on NC size, capping ligand, inter-NC spacing, and long range order; (4) Understanding charge separation and transport in binary NC superlattices; and (5) Incorporating good candidate materials into solar cells to demonstrate improvements in efficiency that result from carefully designed NC architectures. This work will address the challenge of maintaining quantum-confined NC photophysics while also enabling long range charge transport necessary for devices. PI Baxter?s expertise in ultrafast spectroscopy and solar cells and PI Murray?s expertise in synthesis of NCs and superlattices make the team well-equipped to carry out this work.The understanding of fundamental photophysical processes such as interfacial charge transfer, recombination, and inter-NC transport in NC superlattices developed here can be applied to create high-efficiency NC solar cells. Availability of efficient, low-cost, clean, and sustainable solar cells made from earth-abundant, non-toxic materials would transform the US energy portfolio. This project will result in the education and training of two Ph.D. students and multiple undergraduates. Additionally, PI Baxter is developing new courses on "Fundamentals of Solar Cells" and lab-based "Nanomanufacturing for Energy Applications" for students from both universities. Outreach will extend to K-12 students by the PIs? continued participation in NanoDay@Penn, Philly Materials Day at Drexel, and mentoring local high school teachers through NSF RET and university programs. These programs are particularly beneficial for underrepresented groups since they target students and teachers from the School District of Philadelphia, whose student body is over 80% minorities.

PI：Baxter，Jason / Murray，ChristopherPropopals编号：1333649 / 13335821Institution：Drexel大学 /宾夕法尼亚大学 /宾夕法尼亚大学：协作研究：超快载体动力学的半导体纳米晶体固定细胞classclose solar solar solar solarclose-classclose classclose-classclose-classclose-classclose-classcclose classclose classclose clansclose clate clanscclose clansclose clansclose and量子的量子或量子量的量子，或量子相互作用的量子限制材料中光诱导的电荷和能量转移的基本研究。 NCS的材料，直径和排列可用于调整NC间耦合以利用单个NCS的特性和固体的远距离效应。 The emergent optical, electronic, and thermal properties of NC superlattices may lead to transformational improvements in applications including photovoltaics, photonics, and thermoelectrics.The broad objectives of this proposal are (1) to understand ultrafast charge carrier generation, separation, recombination, and transport phenomena in semiconductor nanocrystal superlattices, and (2) to control these fundamental photophysical processes to改善太阳能电池性能。具体而言，我们将研究CDSE，CDTE和CU2ZNSNS4（CZTS）NCS的膜。 CDSE和CDTE NC是出色的模型系统，因为它们的合成和光学性能是众所周知的，可以对玻璃阵列中的载体动力学以及单个单分散NC物种以及二进制NC超级格子的基本超快研究。 CZTS NCS为高效光伏电动机提供了令人兴奋的新方向，该方向是由无毒的，丰富的元素制成的。 PI将完善单分散CZTS NC的合成，以实现有意义的超快光谱表征。该方法以时间分辨的Terahertz光谱（TRTS）和ftstosecond的可见/红外瞬时吸收（TA）为中心，以探测内内和界面的过渡。 THZ光谱法是电子材料的理想的非接触式探针，因为半导体中的THZ频率状态（0.1-3 THz）支架典型的载流子散射速率。 THZ光谱法在区分激子和自由载体的能力方面是独一无二的，并在子picosecond到纳米时间尺度上测量其动力学，为我们的稳态场效应晶体管（FET）测量提供了极好的补充。泵探针TRT和TA是研究光激发载体在自然时间和能量尺度上的界面电荷转移，重组和NC间传输动力学的理想技术。这项工作将提高我们对NCS和NC Suprattices中超级激发激素和自由载体动态的物理现象的理解。 具体研究将包括：（1）确定NC超晶格中电荷转运的机制，例如通过扩展状态或通过激活跳动； （2）测量单个单分散NC物种的超晶格中NC间耦合，界面电荷转移和远程电荷传输的动力学； （3）确定动力学和传输机制对NC大小，封盖配体，Inter-NC间距和远距离顺序的依赖性； （4）了解二进制NC超晶格中的电荷分离和运输； （5）将良好的候选材料纳入太阳能电池中，以证明由精心设计的NC体系结构导致的效率提高。这项工作将应对维持量子限制的NC光体物理学的挑战，同时还可以使设备所需的远距离电荷运输。 Pi Baxter在超快光谱和太阳能电池方面的专业知识以及Pi Murray在NC和超级晶格的合成方面的专业知识，使团队能够很好地进行这项工作。对基本的光物理过程的理解，例如界面电荷转移，重新分配，重新分配，NC Inter-NC在NC超级启动中的运输量都可以创建高效果。通过含有地球的无毒材料制成的有效，低成本，清洁和可持续的太阳能电池的可用性将改变美国的能源组合。该项目将导致两个博士学位的教育和培训。学生和多个大学生。此外，Pi Baxter正在针对两所大学的学生开发有关“太阳能电池基础”和基于实验室的“用于能源应用的纳米制造”的新课程。外展活动会扩展到PIS的K-12学生吗？继续参加Drexel的Nanoday@Penn，Philly Material Day，并通过NSF RET和大学课程指导当地的高中老师。 这些计划对代表性不足的群体特别有益，因为它们针对费城学区的学生和老师，他们的学生团体超过80％。