Heavy Metal Free Quantum Dot Inks for Near to Mid-Wave Infrared Detection

High fabrication costs resulting from the complex processes of high-temperature epitaxy and hybridization have traditionally restricted the use of infrared cameras to military and defense applications (1). However, in the past decade, researchers have been investigating low-cost alternatives using colloidal quantum dots (cQD) to facilitate the adoption of these devices in the commercial detector market. Historically, this field has relied on toxic heavy metal compounds like mercury (Hg) and lead (Pb), which are now facing stricter regulations in consumer electronics across different regions (2,3).<br/><br/>In our study, we introduce a novel approach, utilizing Silver Selenide (Ag₂Se), a material composed of RoHS-compliant elements that are readily available for commercial applications. Our innovation lies in the development of a near-infrared photoconductive (&lt;1600 nm) cQD ink using a variety of different ligands, now common amongst the Pb and Hg inks but not previously documented for Ag₂Se. A framework to extend these dots into the mid-wave via an intraband transition will be presented (4,5). Additionally we explore recent developments in Silver Telluride (Ag₂Te) by extending our approach to this material as well (6).<br/><br/>Lastly, we will highlight some preliminary work on integrating mesoporous transport layers and infrared transparent metal contacts with these cQD detectors to enhance light absorption and improve detector performance.<br/><br/><br/><b>References:</b><br/><br/>1) Pedjovic, V. Infrared Colloidal Quantum Dot Image Sensors - IEEE Xplore. https://ieeexplore.ieee.org/document/9656610/. <br/>2) Gréboval, C.; Chu, A.; Goubet, N.; Livache, C.; Ithurria, S.; Lhuillier, E. Mercury Chalcogenide Quantum Dots: Material Perspective for Device Integration. Chemical Reviews 2021, 121 (7), 3627–3700. DOI:10.1021/acs.chemrev.0c01120. <br/>3) Compliance Faqs: RoHS. https://www.nist.gov/standardsgov/compliance-faqs-rohs. <br/>4) Mølnås, H.; Paul, S.; Scimeca, M.; Mattu, N.; Paredes, I.; Rohr, J.; Ravi, V.; Li, L.; Taylor, A.; Sahu, A. Understanding the growth mechanisms of ultrasmall silver selenide quantum dots for short-wave infrared detectors 2023. DOI:10.2139/ssrn.4452187. <br/>5) Scimeca, M. R., Mattu, N., Paredes, I. J., Tran, M. N., Paul, S. J., Aydil, E. S., & Sahu, A. (2021). Origin of Intraband optical transitions in Ag2se colloidal quantum dots. The Journal of Physical Chemistry C, 125(31), 17556–17564. https://doi.org/10.1021/acs.jpcc.1c05371 <br/>6) Wang, Y., Peng, L., Schreier, J., Bi, Y., Black, A., Malla, A., Goossens, S., & Konstantatos, G. Silver telluride colloidal quantum dot infrared photodetectors and image sensors. Nature News. https://www.nature.com/articles/s41566-023-01345-3