Colloidal quantum dots (CQDs) offer promise in flexible electronics, light sensing and energy conversion. These applications rely on rectifying junctions that require the creation of high-quality CQD solids that are controllably n-type (electron-rich) or p-type (hole-rich). Unfortunately, n-type semiconductors made using soft matter are notoriously prone to oxidation within minutes of air exposure. Here we report high-performance, air-stable n-type CQD solids. Using density functional theory we identify inorganic passivants that bind strongly to the CQD surface and repel oxidative attack. A materials processing strategy that wards off strong protic attack by polar solvents enabled the synthesis of an air-stable n-type PbS CQD solid. This material was used to build an air-processed inverted quantum junction device, which shows the highest current density from any CQD solar cell and a solar power conversion efficiency as high as 8%. We also feature the n-type CQD solid in the rapid, sensitive, and specific detection of atmospheric NO2. This work paves the way for new families of electronic devices that leverage air-stable quantum-tuned materials.
Subscribe to Journal
Get full journal access for 1 year
only $4.92 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Shirasaki, Y., Supran, G. J., Bawendi, M. G. & Bulovic, V. Emergence of colloidal quantum-dot light-emitting technologies. Nature Photon. 7, 13–23 (2013).
Sun, L. et al. Bright infrared quantum-dot light-emitting diodes through inter-dot spacing control. Nature Nanotech. 7, 369–373 (2012).
Tang, J. et al. Colloidal-quantum-dot photovoltaics using atomic-ligand passivation. Nature Mater. 10, 765–771 (2011).
Wang, X. et al. Tandem colloidal quantum dot solar cells employing a graded recombination layer. Nature Photon. 5, 480–484 (2011).
Luther, J. M. et al. Schottky solar cells based on colloidal nanocrystal films. Nano Lett. 8, 3488–3492 (2008).
Brown, P. R. et al. Improved current extraction from ZnO/PbS quantum dot heterojunction photovoltaics using a MoO3 interfacial layer. Nano Lett. 11, 2955–2961 (2011).
Ma, W. et al. Photovoltaic performance of ultrasmall PbSe quantum dots. ACS Nano 5, 8140–8147 (2011).
Konstantatos, G. et al. Ultrasensitive solution-cast quantum dot photodetectors. Nature 442, 180–183 (2006).
David, K. K., Lai, Y., Diroll, B. T., Murray, C. B. & Kagan, C. R. Flexible and low-voltage integrated circuits constructed from high-performance nanocrystal transistors. Nature Commun. 3, 1216 (2012).
Lee, J. S., Kovalenko, M. V., Huang, J., Chung, D. S. & Talapin, D. V. Band-like transport, high electron mobility and high photoconductivity in all-inorganic nanocrystal arrays. Nature Nanotech. 6, 348–352 (2011).
Choi, J. H. et al. Bandlike transport in strongly coupled and doped quantum dot solids: A route to high-performance thin-film electronics. Nano Lett. 12, 2631–2638 (2012).
Choi, J. H. et al. In-situ repair of high-performance, flexible nanocrystal electronics for large-area fabrication and operation in air. ACS Nano 7, 8275–8283 (2013).
Sargent, E. H. Colloidal quantum dot solar cells. Nature Photon. 6, 133–135 (2012).
Johnston, K. W. et al. Schottky-quantum dot photovoltaics for efficient infrared power conversion. Appl. Phys. Lett. 92, 151115 (2008).
Pattantyus-Abraham, A. G. et al. Depleted-heterojunction colloidal quantum dot solar cells. ACS Nano 4, 3374–3380 (2010).
Engel, J. H., Surendranath, Y. & Alivisatos, A. P. Controlled chemical doping of semiconductor nanocrystals using redox buffers. J. Am. Chem. Soc. 134, 13200–13203 (2012).
Chang, L-Y., Lunt, R. R., Brown, P. R., Bulović, V. & Bawendi, M. G. Low-temperature solution-processed solar cells based on PbS colloidal quantum dot/CdS heterojunctions. Nano Lett. 13, 994–999 (2013).
Osedach, T. P. et al. Bias-stress effect in 1, 2-ethanedithiol-treated PbS quantum dot field-effect transistors. ACS Nano 6, 3121–3127 (2012).
Zhao, N. et al. Colloidal PbS quantum dot solar cells with high fill factor. ACS Nano 4, 3743–3752 (2010).
Jean, J. et al. ZnO Nanowire arrays for enhanced photocurrent in PbS quantum dot solar cells. Adv. Mater. 25, 2790–2796 (2013).
Strasfeld, D. B., Dorn, A., Wanger, D. D. & Bawendi, M. G. Imaging Schottky barriers and ohmic contacts in PbS quantum dot devices. Nano Lett. 12, 569–575 (2012).
Luther, J. M. & Pietryga, J. M. Stoichiometry control in quantum dots: A viable analog to impurity doping of bulk materials. ACS Nano 7, 1845–1849 (2013).
Lan, X. et al. Self-assembled, nanowire network electrodes for depleted bulk heterojunction solar cells. Adv. Mater. 25, 1769–1773 (2013).
Luther, J. M. et al. Stability assessment on a 3% bilayer PbS/ZnO quantum dot heterojunction solar cell. Adv. Mater. 22, 3704–3707 (2013).
Nozik, A. J. et al. Semiconductor quantum dots and quantum dot arrays and applications of multiple exciton generation to third-generation photovoltaic solar cells. Chem. Rev. 110, 6873–6890 (2010).
Scheele, M. et al. Nonmonotonic size dependence in the hole mobility of methoxide-stabilized PbSe quantum dot solids. ACS Nano 7, 6774–6781 (2013).
Ma, W., Luther, J. M., Zheng, H., Wu, Y. & Alivisatos, A. P. Photovoltaic devices employing ternary PbSxSe1−x nanocrystals. Nano Lett. 9, 1699–1703 (2009).
Engel, J. & Alivisatos, A. P. Postsynthetic doping control of nanocrystal thin films: Balancing space charge to improve photovoltaic efficiency. Chem. Mater. 26, 153–162 (2014).
Ning, Z. et al. Wave-function engineering of CdSe/CdS Core/Shell quantum dots for enhanced electron transfer to a TiO2 Substrate. J. Phys. Chem. C 114, 15184–15189 (2010).
Ip, A. H. et al. Hybrid passivated colloidal quantum dot solids. Nature Nanotech. 7, 577–582 (2012).
Research Cell Efficiency Records by National Renewable Energy Laboratory, version at November 2013. http://www.nrel.gov/ncpv/images/efficiency_chart.jpg
Zhitomirsky, D. et al. N-type colloidal-quantum-dot solids for photovoltaics. Adv. Mater. 24, 6181–6185 (2012).
Tang, J. et al. Quantum junction solar cells. Nano Lett. 12, 4889–4894 (2012).
Ning, Z. et al. Graded doping for enhanced colloidal quantum dot photovoltaics. Adv. Mater. 25, 1719–1723 (2013).
Wei, P., Oh, J. H., Dong, G. F. & Bao, Z. Use of a 1H-benzoimidazole derivative as an n-type dopant and to enable air-stable solution-processed n-channel organic thin-film transistors. J. Am. Chem. Soc. 132, 8852–8853 (2010).
Liu, Y. PbSe Quantum dot field-effect transistors with air-stable electron mobilities above 7 cm2 V−1 s−1. Nano Lett. 13, 1578–1587 (2013).
Shim, M. & Guyot-Sionnest, P. n-type colloidal semiconductor nanocrystals. Nature 407, 981–983 (2000).
Talapin, D. V. & Murray, C. B. PbSe nanocrystal solids for n- and p-channel thin film field-effect transistors. Science 310, 86–89 (2005).
Mocatta, D. et al. Heavily doped semiconductor nanocrystal quantum dots. Science 332, 77–81 (2011).
Koh, W-k. et al. Heavily doped n-type PbSe and PbS nanocrystals using ground-state charge transfer from cobaltocene. Sci. Rep. 3, 2004 (2013).
Voznyy, O. et al. Charge-orbital balance picture of doping in colloidal quantum dot solids. ACS Nano 6, 8448–8455 (2012).
Hassinen, A. et al. Short-chain alcohols strip X-type ligands and quench the luminescence of PbSe and CdSe quantum dots, acetonitrile does not. J. Am. Chem. Soc. 134, 20705–20712 (2012).
Vande Vondele, J. et al. Quickstep: Fast and accurate density functional calculations using a mixed Gaussian and plane waves approach. Comput. Phys. Commun. 167, 103–128 (2005).
Pearson, R. G. Hard and soft acids and bases. J. Am. Chem. Soc. 85, 3533–3539 (1963).
Ning, Z. et al. All-inorganic colloidal quantum dot photovoltaics employing solution-phase halide passivation. Adv. Mater. 24, 6295–6299 (2012).
Burgelman, M., Nollet, P. & Degrave, S. Modelling polycrystalline semiconductor solar cells. Thin Solid Films 361–362, 527–532 (2000).
Liu, H. et al. Tin oxide films for nitrogen dioxide gas detection at low temperatures. Sens. Actuat. B 177, 460–466 (2013).
Barkhouse, D. A. R. et al. Depleted bulk heterojunction colloidal quantum dot photovoltaics. Adv. Mater. 23, 3134–3138 (2011).
Liu, H. et al. Systematic optimization of quantum junction colloidal quantum dot solar cells. Appl. Phys. Lett. 101, 151112 (2012).
Liu, H. et al. Electron acceptor materials engineering in colloidal quantum dot solar cells. Adv. Mater. 23, 3832–3837 (2011).
This publication is based in part on work supported by Award KUS-11-009-21, made by King Abdullah University of Science and Technology (KAUST), by the Ontario Research Fund—Research Excellence Program, and by the Natural Sciences and Engineering Research Council (NSERC) of Canada. We thank Angstrom Engineering, and Innovative Technology, for useful discussions regarding material deposition methods and control of the glovebox environment, respectively. Computations were performed using the BlueGene/Q supercomputer at the SciNet HPC Consortium provided through the Southern Ontario Smart Computing Innovation Platform (SOSCIP). The SOSCIP consortium is funded by the Ontario Government and the Federal Economic Development Agency for Southern Ontario. H.D. would like to acknowledge financial support from the China Scholarship Council (CSC). The authors thank Larissa Levina for the assistance with CQDs synthesis, S. M. Thon, A. H. Ip and M. Adachi for helpful discussions, S. Masala and J. McDowell for measurement assistance, and E. Palmiano, R. Wolowiec and D. Kopilovic for their help during the course of study. We thank L. Goncharova for assistance with RBS measurements.
The authors declare no competing financial interests.
About this article
Cite this article
Ning, Z., Voznyy, O., Pan, J. et al. Air-stable n-type colloidal quantum dot solids. Nature Mater 13, 822–828 (2014). https://doi.org/10.1038/nmat4007
Recent Progress of Quantum Dot‐Based Photonic Devices and Systems: A Comprehensive Review of Materials, Devices, and Applications
Small Structures (2021)
ACS Energy Letters (2021)
High-Performance Electron-Transport-Layer-Free Quantum Junction Solar Cells with Improved Efficiency Exceeding 10%
ACS Energy Letters (2021)
Journal of Materials Chemistry C (2021)
Stability enhancement of PbS quantum dots by site-selective surface passivation for near-infrared LED application
Nano Research (2021)