High-efficiency colloidal quantum dot infrared light-emitting diodes via engineering at the supra-nanocrystalline level

• Published in: Nature nanotechnology Vol. 14; no. 1; pp. 72 - 79
• Main Authors: Pradhan, Santanu, Di Stasio, Francesco, Bi, Yu, Gupta, Shuchi, Christodoulou, Sotirios, Stavrinadis, Alexandros, Konstantatos, Gerasimos
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 01.01.2019
• Subjects: Density; Efficiency; Energy conversion efficiency; Infrared radiation; Light emitting diodes; Luminescence; Nanocomposites; Open circuit voltage; Organic light emitting diodes; Photoluminescence; Photons; Photovoltaic cells; Quantum dots; Quantum efficiency; Solar cells; Synergistic effect; Thin films
• ISSN: 1748-3387; 1748-3395
• DOI: 10.1038/s41565-018-0312-y

Colloidal quantum dot (CQD) light-emitting diodes (LEDs) deliver a compelling performance in the visible, yet infrared CQD LEDs underperform their visible-emitting counterparts, largely due to their low photoluminescence quantum efficiency. Here we employ a ternary blend of CQD thin film that comprises a binary host matrix that serves to electronically passivate as well as to cater for an efficient and balanced carrier supply to the emitting quantum dot species. In doing so, we report infrared PbS CQD LEDs with an external quantum efficiency of ~7.9% and a power conversion efficiency of ~9.3%, thanks to their very low density of trap states, on the order of 10  cm , and very high photoluminescence quantum efficiency in electrically conductive quantum dot solids of more than 60%. When these blend devices operate as solar cells they deliver an open circuit voltage that approaches their radiative limit thanks to the synergistic effect of the reduced trap-state density and the density of state modification in the nanocomposite.