Tuning the Photoluminescence and Carrier Multiplication Properties in Ultrathin 2D PbS Nanoplatelets

Jannika Lauth^a, Francisco Manteiga Vázquez^a, Ryan W. Crisp^a, Sachin Kinge^b, Arjan J. Houtepen^a, Laurens D. A. Siebbeles^a

^aDelft University of Technology, The Netherlands, Julianalaan, 136, Delft, Netherlands

^bToyota Motor Europe, Hoge Wei 33, B-1930 Zaventem, Belgium

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe September Meeting 2017 (NFM17)

SE2: Opto-electronics of 2-D Nanostructured Semiconductors: Parabolic vs. Linear Dirac Bands

Barcelona, Spain, 2017 September 4th - 9th

Organizers: Daniel Vanmaekelbergh and Cherie Kagan

Oral, Jannika Lauth, presentation 084
Publication date: 20th June 2016

2D semiconductors with tunable band gaps are highly promising materials for ultrathin electronics. Their dimensionality-dependent optoelectronic properties differ significantly from their 0D and 1D counterparts holding high potential for LEDs, photodetectors and solar cells.

2D PbS nanosheets in particular have been investigated due to their thickness-dependent band gap and their increasing carrier multiplication (CM) efficiency with decreasing nanosheet thickness.[1-2] However, up to now, only few colloidal synthesis ways exist to produce 2D PbS with a thickness approaching few atomic layers (1-2 nm).[3-4] We present a low temperature, acetate-free synthesis of colloidal PbS nanoplatelets (thickness 1.5 nm) that exhibit a significantly blue-shifted band gap (683 nm, 1.8 eV) and zero photoluminescence (PL). By surface passivation of the pristine PbS nanoplatelets with different metal halides, we can boost their PL from 705 nm (1.75 eV), only slightly Stokes-shifted to the absorption edge, up to 750 nm (1.65 eV).

We use ultrafast optical-pump terahertz probe spectroscopy to probe the share of excitons and free charges formed under photoexcitation in strongly confined PbS nanoplatelets and to determine if the CM threshold in ultrathin PbS nanoplatelets is decreased as predicted. This would significantly improve the efficiency of CM in 2D PbS structures.

[1] Bielewicz, T.; Dogan, S.; Klinke, C., Small 2015, 11, 826-833.

[2] Aerts, M.; Bielewicz, T.; Klinke, C.; Grozema, F. C.; Houtepen, A. J.; Schins, J. M.; Siebbeles, L. D. A., Nat. Commun. 2014, 5, 3789.

[3] Khan, A. H.; Brescia, R.; Polovitsyn, A.; Angeloni, I.; Martín-García, B.; Moreels, I., Chem. Mater. 2017, 29, 2883-2889.

[4] Lauth, J.; Vázquez, F. M.; Crisp, R. W.; Kinge, S.; Houtepen, A. J.; Siebbeles, L. D. A., in preparation 2017.

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