Heterovalent Cation Dopant Incorporation in PbS Colloidal Quantum Dots- What Drives it?

Alexandros Stavrinadis^a, Gerasimos Konstantos^a, Jacopo Stefano Pelli Cresi^b, Federico Bocherini^b, Francesco d’Acapito^c

^aICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Avinguda Carl Friedrich Gauss, 3, Castelldefels, Spain

^bUniversity of Bologna, Department of Physics and Astronomy, viale C. Berti Pichat 6/2, Bologna, Italy

^cIOM-CNR, OGG, c/o ESRF, 38043 Grenoble

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe September Meeting 2015 (NFM15)

Santiago de Compostela, Spain, 2015 September 6th - 15th

Poster, Alexandros Stavrinadis, 048
Publication date: 8th June 2015

Doping colloidal quantum dots with heterovalent cations is of great interest for a variety of optoelectronic applications since it can enable control over the dots´ charge carrier type, concentration and dynamics. It may also potentially lead to new and exotic optical functionalities of CQDs such as the appearance of intra-band absorption in the mid IR optical region upon successful charging of the dots. Towards that purpose, it is necessary to understand what drives the incorporation of a cation dopant in the CQD´s lattice and in particular doping by cation substitution. Understanding that is even more important considering that doping can arise from a variety of incorporation mechanisms such as positioning of the dopant on the surface of the dots, interstitial doping, remote doping due to the formation of secondary phases etc. In this work we report a significant relationship between solubility of the dopant in the host structure as this is known from bulk semiconductor alloys, with what actually happens in the case of 3-3.5 nm PbS CQDs. By comparing EXAFS, ICP-OES, XRD, Optical absorption and photoluminescence properties of PbS CQDs with trivalent dopants that are similar in many ways apart of their ability to dissolve in bulk PbS, we further investigate the impact of doping by substitution to the structure, optical and electronic properties of the dots. We further correlate macroscopic effects of doping to structural effects resolved at the single dot level. Finally we show n-type functionality for a successful dopant incorporation case.

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