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

Abstract

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 1014 cm−3, 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.

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Fig. 1: Device structure and composition of the LEDs based on binary and ternary blends.
Fig. 2: Performance of LED devices.
Fig. 3: PLQE and PL dynamics of QD blends.
Fig. 4: PV performance, quantified trap-state analysis via TAS and VOC dependence of the single, binary and ternary QD blend devices.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

The authors acknowledge financial support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 725165), the Spanish Ministry of Economy and Competitiveness (MINECO) and the ‘Fondo Europeo de Desarrollo Regional’ (FEDER) through grant TEC2017-88655-R. The authors also acknowledge financial support from Fundacio Privada Cellex, the program CERCA and from the Spanish Ministry of Economy and Competitiveness through the ‘Severo Ochoa’ Programme for Centres of Excellence in R&D (SEV-2015-0522). F.D.S. and S.C. acknowledge support from two Marie Curie Standard European Fellowships (NANOPTO, H2020-MSCA-IF-2015-703018 and NAROBAND, H2020-MSCA-IF-2016-750600).

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G.K. proposed the idea and directed the study. S.P. co-developed the concept, fabricated and characterized the devices, and analysed the data. S.P. and G.K. designed the experiments with the help of F.D.S. F.D.S. performed the PLQE and electroluminescence studies and processed the results. Y.B. and S.G. synthesized the materials. S.C. performed the TEM imaging. A.S. performed the scanning electron microscopy imaging. G.K. and S.P. wrote the manuscript with input from the co-authors.

Corresponding author

Correspondence to Gerasimos Konstantatos.

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G.K. and S.P. have filed a patent application related to this work.

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

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Pradhan, S., Di Stasio, F., Bi, Y. et al. High-efficiency colloidal quantum dot infrared light-emitting diodes via engineering at the supra-nanocrystalline level. Nature Nanotech 14, 72–79 (2019). https://doi.org/10.1038/s41565-018-0312-y

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