PbS nanocrystal growth and overgrowth by thiourea precursors
Wolfgang Heiss a, Niall Killilea a, Mykhailo Sytnyk a
a Friedrich-Alexander-Universität Erlangen-Nürnberg, Institute Materials for Electronics and Energy Technology, Department of Materials Science and Engineering, Energy Campus Nürnberg, Fürther Straße, 250, Nürnberg, Germany
Proceedings of Online nanoGe Fall Meeting 20 (OnlineNFM20)
#INfraNC20. Infrared Nanocrystals
Online, Spain, 2020 October 20th - 23rd
Organizers: Emmanuel Lhuillier and Philippe Guyot-Sionnest
Invited Speaker, Wolfgang Heiss, presentation 214
Publication date: 4th October 2020

Colloidal nanocrystals from PbS are most prominent materials for applications in optoelectronic devices operating in near to mid-infrared. Traditionally, they are synthesized by a hot injection method based on bis(trimethylsilyl) sulfide used as sulfur precursor. More recently Hendricks et al. [1] introduced a library of substituted thio-ureas as sulfur precursors of varying reactivity that can be used for size tuning. We combined these two approaches and selected a disubstituted thiourea compound as sulfur precursor and show the growth [2] and overgrowth of colloidal nanocrystals with this precursor. The advantage of this method is, that we can obtain controlled growth over infinitely large substrates, over all the nanocrystal size range towards bulk material (Figure 1). With the thio-urea precursor homo-epitaxial growth is achieved as well as heteroepitaxial growth, certainly related to the lattice matching between the substrate and the overgrowing PbS crystal. The obtained materials are of excellent quality and based on the nanocrystals grown from the thiourea precursor, photoconducting devices are demonstrated with band gap energies reaching those of the bulk material. The nanocrystals were also applied in photovoltaic devices providing record like behavior, especially for relatively long wavelengths [3]. Thus the growth of optoelectronic structures form thiourea precursors in organic solvents represents a versatile and promising rout for the low cost fabrication of infrared-optoelectronic devices.

We aknowledge financial support from the Deutsche Forschungsgemeinschaft via project 404984854 and the GRK2495/J. 

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