Engineering All-Inorganic Quantum Dot Heterojunction Photovoltaics Through Surface Chemical Manipulations

PI: Kagan， cherie提案号：1236406机构：宾夕法尼亚大学通过表面化学操作来设计全无机量子点异质结光伏技术曲面半导体量子（QDs）有望成为低成本、大面积、高性能的太阳能光伏（pv），因为它们可以像墨水一样从溶液中加工，并且它们具有尺寸、形状和成分相关的独特电子和光学特性，允许从纳米级构建块中设计和制造全无机材料。挑战在于如何在固体薄膜中利用这些可溶液处理的量子点的宝贵电子特性，在固体薄膜中，为了设计高效太阳能pv的结，以及更广泛地用于半导体电子和光电子器件，需要容易的电荷传输和掺杂。大面积的表面（体积比）、化学计量平衡和量子点之间的耦合极大地影响了量子点固体薄膜中的载流子类型和输运。本项目将通过化学转化来控制固态薄膜中量子点的表面化学和化学计量学，同时原位探测其表面化学和电学性质，以设计高迁移率的n型和p型量子点薄膜以及高效的pn异质结pv。例如，湿化学合成方法可以产生宏观数量的胶体半导体量子点，这些量子点可以在尺寸、形状和成分上进行定制，并像墨水一样通过自旋铸造和浸渍涂层沉积，形成大面积、均匀的量子点薄膜。在这里，PI将使用最近开发的硫氰酸铵处理交换薄膜中的量子点，形成强电子耦合和几乎裸露的量子点，为随后的化学转化提供位点。电化学、光学和电学测量将用于表征能级和载流子类型、捕获和迁移率，因为我们修饰QD薄膜。高迁移率、长载流子寿命的量子点薄膜将被集成到太阳能电池中，并被优化成宽带、高吸收的量子点薄膜，用于高效太阳能光伏电池。提出的研究活动将加深对表面、化学计量和外在原子在弱量子受限、更宽带隙和更强量子受限、更小带隙量子点中的作用的理解。表面的作用对于设计高载流子迁移率，n和p型材料非常重要，这些材料不仅影响太阳能光伏发电，而且影响广泛的可持续电子和光电子器件的设计；低功率电子器件、能量收集热电器件和低功率发光二极管；从溶液可加工的量子点材料。基本的理解和技术的发展将扩展纳米结构材料的知识和教学，以及化学转化和材料设计的过程，适用于不断增长的纳米结构材料工具箱。该项目将为本科生和研究生提供跨学科的研究经验。它还将为学生和PI提供一个机会，通过演示、演讲和正式的校外课程，与K-12学生和教师、公众和科学界分享可持续发展和纳米技术的科学和工程。

PI: Kagan, CherieProposal Number: 1236406Institution: University of PennsylvaniaTitle: Engineering All-Inorganic Quantum Dot Heterojunction Photovoltaics Through Surface Chemical ManipulationsColloidal semiconductor quantum (QDs) promise low-cost, large-area, high performance solar photovoltaics (PVs) as they may be processed from solution like inks and they have size, shape, and composition-dependent electronic and optical properties uniquely allowing the design and fabrication of all-inorganic materials from nanoscale building blocks. The challenge is to harness the prized electronic properties of these solution-processable QDs in solid thin films where facile charge transport and doping are required to engineer junctions for efficient solar PVs and more broadly for semiconductor electronic and optoelectronic devices. The large area surface (to volume), stoichiometric balance, and coupling between QDs greatly affect charge carrier type and transport in QD solid thin films. This project will carry out chemical transformations to manipulate the surface chemistry and stoichiometry of QDs in solid state thin films while probing in-situ their surface chemistry and electrical properties to design high mobility, n- and p-type QD thin films and high efficiency pn heterojunction PVs. For example, wet-chemical synthetic methods yield macroscopic quantities of colloidal semiconductor QDs that may be tailored in size, shape, and composition and deposited like inks by spin- casting and dip-coating to form large-area, uniform QD thin films. Here, the PI will exchange the QDs in thin films using the recently developed ammonium thiocyanate treatment to form strongly electronically coupled and nearly bare QDs, providing sites for subsequent chemical transformations. Electrochemical, optical and electrical measurements will be used to characterize the energy levels and carrier type, trapping, and mobility as we modify QD films. High mobility, long carrier lifetime QD films with electronic structures tailored to define large junction offsets will be integrated into solar cells and optimized to form broad band, high absorption QD films for efficient solar PVs.The proposed research activities will develop understanding of the role of surface, stoichiometry, and extrinsic atoms in weakly quantum confined, wider band gap and more strongly quantum confined, smaller band gap QDs. The role of the surface is important in designing high carrier mobility, n- and p-type materials that impact not only solar photovoltaics, but the design of a broad range of sustainable electronic and optoelectronic devices; low-power electronics, energy harvesting thermoelectrics, and low-power light-emitting diodes; pursued from solution-processable QD materials. The fundamental understanding and technological developments will expand knowledge and teaching of nanostructured materials and of processes for chemical transformations and design of materials, applicable to the growing toolbox of nanostructured materials. The program will provide an interdisciplinary research experience for undergraduate and graduate students. It will also provide an opportunity for the students and PI to share the science and engineering of sustainable and nanoscale technologies with K-12 students and teachers, the public, and the scientific community through demos, presentations, and formal and extramural coursework.