GOALI: Additive and Stoichiometry Engineering in Perovskites: Building Deeper Understanding of the Impact on Optoelectronic Properties for Energy Applications

半导体行业面临的一个关键挑战是为更便宜、更好性能和更普遍的电子和能源技术开发新的材料和设备，包括太阳能电池、发光设备和用于计算的存储器/逻辑。在过去的十年里，“钙钛矿”半导体家族取得了巨大的进步，它既提供了高器件性能的前景，又具有超廉价制造的潜力。例如，钙钛矿太阳能电池的功率转换效率(一个关键的性能指标)在前所未有的短时间内从3%上升到25%以上，钙钛矿组件的加工是使用简单和廉价的溶液涂层方法实现的。实现这一进展的一个关键方面是对钙钛矿成分的微小变化或外来成分的添加如何改善钙钛矿材料的形成或器件性能的经验研究。虽然取得了业务上的进展，但改进的机制还没有得到普遍的理解。该项目涉及大学(杜克大学)和行业(IBM公司)的联合合作，重点是使用最先进的制造和表征技术来探索钙钛矿材料和器件中成分修饰的影响。这项研究的目标是提高理解，使设计和演示性能更好的能源和电子设备成为可能。该项目还为本科生、研究生和博士后研究人员提供了一个宝贵的机会，通过与IBM的积极合作来体验工业研究。与杜克共享材料仪器基金的合作也开辟了一条途径，让广泛的年轻和非专业学生接触到与项目相关的概念和STEM机会。最近的钙钛矿型太阳能电池文献提供了过多的新配方和加工技术来提高性能。尽管太阳能电池性能被广泛用于判断添加剂/化学计量比相对于目标目标的有效性，但这种器件结构复杂，可能隐藏对钙钛矿传输/复合特性(例如，载流子密度、迁移率、复合寿命和扩散长度)的内在影响。该项目的目标是深入研究钙钛矿薄膜中的化学计量比变化和三种添加剂(聚合物、富勒烯和分子掺杂剂)，以更全面地了解材料和器件改进所涉及的过程，并推动成分工程的发展。通过大学(杜克大学)和工业界(IBM公司)的合作，这项研究的目的是：1)澄清添加剂的位置并评估钙钛矿薄膜中的化学计量调制；2)使用(由Goali合作伙伴IBM开发的)新开发的先进测量--即载流子分辨的光霍尔--以及其他表征方法(例如，电流-电压、导纳光谱、光致发光、光电发射)，确定添加剂和化学计量变化对载流子密度和传输/复合性能的影响；3)最终通过设备制造/表征验证性能和稳定性的改进。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

A key challenge for the semiconductor industry is to develop new materials and devices for cheaper, better performing and more pervasive electronic and energy technologies, including solar cells, light-emitting devices and memory/logic for computation. Over the last ten years, tremendous progress has been demonstrated for the “perovskite” semiconductor family, which offers the promise of both high device performance and potential for ultra-cheap fabrication. As an example, power conversion efficiencies (a key performance metric) for perovskite solar cells has risen from 3 to more than 25 percent over an unprecedented short period of time, and processing for the perovskite component is achieved using simple and cheap solution coating methods. A critical aspect enabling this progress has been the empirical study of how small variations in perovskite composition or additions of foreign components can improve perovskite material formation or device performance. While operational advancements have been made, the mechanism of improvement is not generally understood. This project involves a joint university (Duke) – industry (IBM Corp) collaboration and focuses on using state-of-the-art fabrication and characterization techniques to explore the impact of compositional modifications in perovskite materials and devices. The research targets improved understanding to enable design and demonstration of better performance energy and electronic devices. The project further provides a valuable opportunity for undergraduate, graduate and postdoctoral researchers to experience industrial research through active collaboration with IBM. A partnership with the Duke Shared Materials Instrument Facility also opens a pathway to expose a broad range of younger and non-specialist students to project-related concepts and STEM opportunities. Recent perovskite solar cell literature provides a plethora of new recipes and processing techniques to improve performance. Although solar cell performance is widely used to judge effectiveness of additives/stoichiometry relative to targeted goals, such device structures are complex and may hide intrinsic impacts on perovskite transport/recombination properties (e.g., carrier density, mobility, recombination lifetime and diffusion length). This project targets in depth studies on stoichiometry variations and three classes of additives (polymers, fullerenes and molecular dopants) within perovskite films to more fully understand processes involved in material and device improvement and to push the boundaries of compositional engineering. Through a university (Duke) – industry (IBM Corp) collaboration, the research aims to: 1) Clarify the location of the additives and assess stoichiometry modulation within the perovskite films; 2) determine the impact of additives and stoichiometry variation on carrier density and transport/recombination properties using a newly developed (by GOALI partner IBM) advanced measurement—i.e., carrier-resolved photo-Hall—as well as other characterization approaches (e.g., current-voltage, admittance spectroscopy, photoluminescence, photoemission); and 3) ultimately validate performance and stability improvements through device fabrication/characterization.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.