Surface and Interface Effects on Photovoltaic and Light-Emitting Characteristics of Colloidal Nanocrystal Heterostructures

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Nontechnical Description: Semiconductors have enabled numerous technologies including computers, solar cells and LED lighting. The emerging ability to make semiconductor materials sufficiently small such that varying their size and shape drastically alters their optical and electrical properties is paving new paths to improving device efficiencies and, more importantly, imparting them with new capabilities. This project examines and improves on such semiconductors that can be synthesized and processed by relatively simple means, using chemical solutions. These materials can enable new or multiple functions in devices, for example, allowing a pixel in a display screen to not only emit but also sense light. Such a capability may in turn simplify the design and manufacturing of electronics such as smart phones and tablets, to imbue them with multiple new functionalities while reducing their size, weight, and energy consumption. Multi-faceted challenges to be tackled here provide ample educational and training opportunities for the students involved, helping them be better prepared to become leaders in interdisciplinary science and engineering fields. The PI is committed to building on the research results of this project to enhance teaching and promote benefits of emerging science and technologies to the general public.Technical Description: Colloidal quantum dots and, in particular, their heterostructures that can be processed through simple solution means are generating new opportunities through simplified fabrication processes, improved device performance and new functional capabilities. Central to incorporating these materials into electronic/optoelectronic devices is the understanding of how their surfaces and interfaces affect placement of charge carriers in and out of these materials. In turn, exploiting different surfaces/interfaces to control these fundamental processes and therefore improve device characteristics is essential in paving the path to the next generation of devices incorporating emerging nanoscale materials. This project examines critical surface and interfacial factors that impact photovoltaic and electroluminescence characteristics of devices consisting of colloidal quantum dots and in particular, their anisotropic heterostructures. Varying composition and shape provides a deeper understanding of the interplay between surface/interface effects, the underlying band structure, and shape/anisotropy. The knowledge gained should be broadly applicable to designing new materials with appropriate surfaces and interfaces for radically improved device performance and capabilities. The research endeavors of this project are synergistic with education and outreach efforts. Research findings inspire teaching and mentoring activities, impacting education while also promoting interest in fundamental science among the general public.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.