Optoelectronic devices operating in the infrared region are of utmost importance, crosscutting different fields with applications in energy harvesting, gas sensing, night vision, and medical diagnosis. Present-day infrared technologies rely on high-quality epitaxially grown semiconductors, such as III-V materials. This materials platform is incompatible with CMOS technology that underpins modern consumer electronics. Alternatives to conventional materials are expected to bring new functionalities to the consumer market.
Colloidal quantum dots, solution-processed semiconductor nanocrystals, offer a powerful platform for infrared applications. Their optoelectronic properties can be widely tuned by changing the size and surface chemistry, and they allow for low-temperature deposition from solution over large areas using available manufacturing. These enable their integration in many systems such as multi-junction photovoltaics to complement the performance of silicon solar cells, as well as light sources and photodetectors.
In this talk, I will present some examples of the use of quantum dots as a building block for high-performance optoelectronic devices. Firstly, I will introduce novel surface engineering strategies to produce printable quantum dot inks that enable single-junction quantum dot solar cells with a certified record power conversion efficiency. I will also show their potential to complement silicon photovoltaics and electrode engineering strategies to improve device performance. Secondly, I will present the liquid-phase heteroepitaxial growth of inorganic perovskite around quantum dots. This work demonstrates, for the first time, that lattice matching between solution-processed semiconductors contributes to materials stability exceeding that of each constituent. The new combination of materials enables the realization of electronic properties not available in the single-phase constituents. I will then discuss the recent work on nanoscale exciton dynamics and transport in hybrid structures. This work – using the state-of-the-art transient absorption microscopy – provides fundamental insights into the transport mechanism at hybrid interfaces and guides the materials design for future optoelectronics. Finally, I will conclude my talk with an outlook on solution-processed hybrid structures towards infrared light sources and photodetectors.
Mengxia Liu is currently a post-doctoral fellow in the Cavendish Laboratory at the University of Cambridge. She received her PhD degree in the Department of Electrical and Computer Engineering at the University of Toronto in 2018. Her research focuses on developing solution-processed infrared optoelectronic materials and devices. Her studies involve novel materials design, device manufacturing, and ultrafast spectroscopies.
Mengxia’s work has been published in top tier peer-reviewed journals, including Nature, Nature Materials, Nature Energy, and Joule. She is an MIT EECS Rising Star; a Review Editor for the Frontiers in Energy Research; a recipient of 2019 Marie Skłodowska-Curie Actions Seal of Excellence Award, 2018 Chinese Government Award for Outstanding Self-Financed Students Abroad, and 2015-2018 Hatch Graduate Scholarship. She served as a co-organizer of QD2018 – the biannual international conference on quantum dots – and chaired plenary talks.