Emission of Precipitation Deposited PbS Quantum Dots on Polyethylene Terephthalate
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Emission of Precipitation Deposited PbS Quantum Dots on Polyethylene Terephthalate Bruno Ullrich*, Andrew R. Markelonis, Joanna S. Wang, and Gail J. Brown Air Force Research Laboratory, Materials & Manufacturing Directorate, Wright Patterson AFB, OH 45433-7707, USA
ABSTRACT Centrifuge enforced precipitation was used to disperse PbS quantum dots (diameter 4.7 nm) on polyethylene terephthalate. By employing double frequency Fourier transform spectroscopy, we studied the emission properties of the sample. Gaussian shaped emission spectra from cryogenic temperatures up to room temperatures were observed, demonstrating the potential of PbS quantum dots to be used as light emitters in combination with organic matrices. One interesting feature is that the linewidth of the emission spectrum does not follow the expected thermal broadening. INTRODUCTION Starting in the 1970s, composites of various inorganic semiconductors, which fulfill certain required technological functionalities, have been developed, further matured, and successively employed in mass-market electronic and optoelectronic devices [1,2]. These heterogeneous materials revolutionized nearly all areas of life. More recently, cost effective chemically tailored hybrids, i.e., the combination of organic and inorganic semiconductors – attributed as a marriage of convenience - attracted growing research interest about ten years ago [3,4]. Boosted by the envisaged technological impact of hybrid nanoscience, the research focused on the chemical bonding essentials of inorganic (metals and semiconductors) quantum dots (QDs) on polymetric surfaces and the embedding in polymer matrices [5,6]. The production of polymer-inorganic nanocomposites (PINCs) is equally motivated by economical and technological reasons [7], i.e., the fairly low production costs of polymers, their intrinsic capability of “free-shaping” combined with their low-weight and elasticity are an extremely attractive host for inorganic additives in the form of QDs. Various methods are used to produce PINCs: synthetic techniques, physical methods, electrochemical formation, chemical vapor deposition, and electrophoretic deposition [7-9]. Given that photoluminescence (PL) is the prerequisite for light emitting device structures, the PL properties of various QDs, such as CdS, CdTe [10,11], and PbS [12-14], have been intensively studied. The clearly enhanced quantum confinement with respect to most III-V and II-VI compound semiconductors [15], explains the explicit interest in QDs of the IV-VI semiconductor PbS. In this article, we present our first attempt to form light emitting colloidal PbS QD films on polyethylene terephthalate (PET). EXPERIMENTAL DETAILS A commercial solution of 4.7 nm PbS QDs in toluene with oleic acid as ligands was used to fabricate the sample, i.e., 12.5 L of the PbS QDs in a toluene solution (40 mg/mL) with oleic acid as capping reagents were added to 5 mL ethanol in an 8 mL sample vial with the PET substrate on the bottom. The deposition of the particles from the solution was enfor
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