Impact of Different Surface Ligands on the Optical Properties of PbS Quantum Dot Solids

Fan Xu; Luis Felipe Gerlein; Xin Ma; Chelsea R Haughn; Matthew F Doty; Sylvain G Cloutier

doi:10.3390/ma8041858

Impact of Different Surface Ligands on the Optical Properties of PbS Quantum Dot Solids

Materials (Basel). 2015 Apr 21;8(4):1858-1870. doi: 10.3390/ma8041858.

Authors

Fan Xu^{1

2}, Luis Felipe Gerlein³, Xin Ma², Chelsea R Haughn⁴, Matthew F Doty⁵, Sylvain G Cloutier^{6

7}

Affiliations

¹ Alphasense, Inc., 510 Philadelphia Pike, Wilmington, DE 19809, USA. xinma@udel.edu.
² Department of Electrical and Computer Engineering, University of Delaware, 140 Evans Hall, Newark, DE 19716, USA. xinma@udel.edu.
³ Technologie Supérieure, 1100 rue Notre-Dame Ouest, Montréal, QC H3C 0J9, Canada. luis-felipe.gerlein-reyes.1@etsmtl.net.
⁴ Department of Materials Science and Engineering, University of Delaware, 201 DuPont Hall, Newark, DE 19716, USA. chelsera@udel.edu.
⁵ Department of Materials Science and Engineering, University of Delaware, 201 DuPont Hall, Newark, DE 19716, USA. doty@udel.edu.
⁶ Department of Electrical and Computer Engineering, University of Delaware, 140 Evans Hall, Newark, DE 19716, USA. sylvaing.cloutier@etsmtl.ca.
⁷ Technologie Supérieure, 1100 rue Notre-Dame Ouest, Montréal, QC H3C 0J9, Canada. sylvaing.cloutier@etsmtl.ca.

Abstract

The engineering of quantum dot solids with low defect concentrations and efficient carrier transport through a ligand strategy is crucial to achieve efficient quantum dot (QD) optoelectronic devices. Here, we study the consequences of various surface ligand treatments on the light emission properties of PbS quantum dot films using 1,3-benzenedithiol (1,3-BDT), 1,2-ethanedithiol (EDT), mercaptocarboxylic acids (MPA) and ammonium sulfide ((NH4)2S). We first investigate the influence of different ligand treatments on the inter-dot separation, which mainly determines the conductivity of the QD films. Then, through a combination of photoluminescence and transient photoluminescence characterization, we demonstrate that the radiative and non-radiative recombination mechanisms in the quantum dot films depend critically on the length and chemical structure of the surface ligands.

Keywords: 1,3-BDT; EDT; MPA; PbS; ammonium sulfide; lead chalcogenide; photo-luminescence; quantum dots; surface ligand.