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Recently the quantum dots (QDs) synthesis from single source precursors (SSPs) showed a potential interest for patterning formation of nano-composites. In this approach the SSPs have to be mixed with a matrix that afterwards is treated selectively to obtain the desired nanocomposite. The study of the generation of the QDs from the SSPs is, therefore, crucial for the definition of its behaviour within the polymeric matrix. The formation of the CdS QDs via thermolysis of the cadmium diethyldithiocarbamate (CdDDTC) was performed and studied in the presence of a non coordinating solvent such as octadecene (ODE) in presence of myristic acid (MA) as ligand. The precursor is then studied in combination with the poly(methyl methacrylate) (PMMA) polymer for the generation of the CdS QDs under the laser irradiation within a film. The effect of the laser has been studied both on neat PMMA and on the polymer/precursor blend film with the aid of the fluorescence microscope. The results are used to identify the optimal laser parameters to obtain the decomposition of the precursor and to evaluate the effect of the laser irradiation on the polymer. © 2017 Elsevier Ltd.

This paper focuses on a preliminary study based on a two-steps approach to produce complex core/multipleshell architectures, such as “dots-in-rods” (DRs), to be exploited as color down-conversion filters for displaymanufacturing. Core/shell CdSe/CdS DRs are prepared by using a conventional fast hot injection reaction method togrow CdS layers onto CdSe QDs cores. Then, the CdSe/CdS DRs are engineered by growing an additional CdS shellcoated by oleate (OA) molecules, thus producing CdSe/CdS@CdS/OA DRs. This further hybrid shell is synthesized bymeans of a seeded-growth approach, consisting of the controlled injection of TOP-S and cadmium oleate (Cd(OA)2) assulfur and cadmium precursors, respectively. As assessed by transmission electron microscopy (TEM) and UV-Visabsorption and photoluminescence (PL) spectroscopies analyses, the feasibility to control the amount of precursorsallows to modulate the thickness of the further hybrid shells and therefore the morphological and optical properties of thefinal heterostructures. The introduction of further shells grafted by specific organic ligand improves the solubility inpolymeric matrices. This condition is crucial to produce hybrid nanocomposite films that can be integrated in displaymanufacturing applications. Moreover, the capability of the final CdSe/CdS@CdS/OA nanostructures to convert bluelight in red wavelengths with a remarkable photoluminescence quantum yields (PLQY) makes the produced materials theideal candidates for a variety of optoelectronic applications, particularly for the fabrication of color down-conversionfilters.

The synthesis of CdSe quantum dots (QDs) from a single source precursor is a known way to form a nanocomposite by its thermal decomposition. Recently, some of them have been used to grow QDs by direct laser patterning. Here, the authors report the study of the formation of the CdSe QDs starting from the decomposition of the 2-(N,N-dimethylamino)ethylselenolate of cadmium dispersed in a polymethylmethacrylate film induced both by heating and laser patterning. The formation of the CdSe QDs under annealing at 150 °C is studied as a function of the precursor concentration and molar ratio with respect to two different QD ligands such as oleic acid and oleylamine. The photoluminescent spectra of the formed nanocomposite show that the oleic acid induces the formation of the direct bandgap, while oleylamine shows only a broadband emission. The laser patterning of the film was carried out with a UV laser (355 nm) with a pulse frequency of 40 kHz and a fluence of 1.06 J/cm2. The resulting patterned areas were characterized by a fluorescence microscope showing the formation of a photoluminescence path only when the ligands were present, suggesting the formation of the functional (photoluminescent) QDs.The synthesis of CdSe quantum dots (QDs) from a single source precursor is a known way to form a nanocomposite by its thermal decomposition. Recently, some of them have been used to grow QDs by direct laser patterning. Here, the authors report the study of the formation of the CdSe QDs starting from the decomposition of the 2-(N,N-dimethylamino)ethylselenolate of cadmium dispersed in a polymethylmethacrylate film induced both by heating and laser patterning. The formation of the CdSe QDs under annealing at 150 °C is studied as a function of the precursor concentration and molar ratio with respect to two different QD ligands such as oleic acid and oleylamine. The photoluminescent spectra of the formed nanocomposite show that the oleic acid induces the formation of the direct bandgap, while oleylamine shows only a broadband emission. The laser patterning of the film was carried out with a UV laser (355 nm) with a pulse frequency of 40 kHz and a fluence of 1.06 J/cm2. The resulting patterned areas were chara...

The production of a Quantum Dots-Light Emitting Diode by Direct Laser Patterning is a new strategy to draw luminous patterns on Organic Light Emitting Diodes. The laser patterned Quantum Dots-Light Emitting Diode improves the optical performances of Organic Light Emitting Diodes introducing Quantum Dots as luminophores and avoids the use of photolithography to draw patterns, thus simplifying the manufacturing process. The purpose of this study is to describe the production of a Quantum Dots-Light Emitting Diode prototype using Direct Laser Patterning technology and to assess its environmental performance, by means of Life Cycle Assessment method, with the aim to identify the hotspots in the production chain and to support a more environmentally-friendly product design. The goal of the Life Cycle Assessment study is to evaluate the environmental impacts of the production of one Quantum Dots-Light Emitting Diode with a surface of 4 cm2 and a laser patterning surface of 25 mm2. The system boundaries were from cradle to gate and included the production of the following elements: the cadmium sulphide precursor for Quantum Dots, the organic electroluminescent polymer, the anode and cathode as well as laser patterning. Primary data were collected at laboratory scale and IMPACT 2002+ impact assessment method was used. Results show that the main hotspots are the production of the electroluminescent polymer and the indium tin oxide glass used as anode. Therefore, other materials could be used as anode and polymer with the aim to improve the environmental performances of the device. Moreover, a comparative analysis between the environmental impacts of the new patterning technology and that of the traditional photolithography shows that their environmental performances are quite similar. However, the use of the new Quantum Dots-Light Emitting Diode technology is advisable because of its better technological performance, lower costs and processing time. © 2016 Elsevier Ltd

In this brief review the advances on Direct Laser Patterning (DLP) for the synthesis of photo-luminescent semiconductor quantum dots (QDs) belonging to II-VI groups, especially in solid state using laser-assisted conversion are reported and commented. The chemistry of the precursor synthesis is illustrated because it is a crucial step for the development of the direct laser patterning of QDs. In particular, the analysis of cadmium (bis)thiolate and cadmium xanthates precursors after thermal and laser treatment is examined, with a special focus on the optical properties of the formed QDs. The second part of the review examines how the laser parameters such as the wavelength and pulse duration may regulate the properties of the patterned QDs. The DLP technique does not require complex laser systems or the use of dangerous chemical post treatments, so it can be introduced as a potential method for the patterning of pixels in quantum dot light emitting diodes (QD-LEDs) for display manufacturing.

The synthesis of colloidal photo-luminescent semiconductor quantum dots (QDs), belonging to II-VI groups, even from single source precursors is presented. Since three decades their synthesis has been pursued implementing new and easier synthetic conditions that standardize their production. In this work is reported the production of luminescent of CdS QDs in a polymeric film induced by laser processing (www.miledi-h2020.eu/). A film of PMMA doped with two types of precursors (cadmium xanthates) is irradiated with an UV laser source with different energy doses. The structured film will then be observed with confocal fluorescent microscope. The interesting results shows that the two different xanthates display a different behavior under the laser source even if their absorption spectrum is similar. The second interesting result is that the effect of the laser is the production luminescent pattern only for certain fluences and that the same film treated with the temperature did not show any luminescence.The synthesis of colloidal photo-luminescent semiconductor quantum dots (QDs), belonging to II-VI groups, even from single source precursors is presented. Since three decades their synthesis has been pursued implementing new and easier synthetic conditions that standardize their production. In this work is reported the production of luminescent of CdS QDs in a polymeric film induced by laser processing (www.miledi-h2020.eu/). A film of PMMA doped with two types of precursors (cadmium xanthates) is irradiated with an UV laser source with different energy doses. The structured film will then be observed with confocal fluorescent microscope. The interesting results shows that the two different xanthates display a different behavior under the laser source even if their absorption spectrum is similar. The second interesting result is that the effect of the laser is the production luminescent pattern only for certain fluences and that the same film treated with the temperature did not show any luminescence.

We acknowledge financial support from FP7 project “Laser Induced Synthesis of Polymeric Nanocomposite Materials and Development of Micro-Patterned Hybrid Light Emitting Diodes (LED) and Transistors (LET)”-LAMP (Project G.A.247928). A.K.B. and I.D.W.S. also acknowledge financial support from EPSRC Programme “Challenging the Limits of Photonics: Structured Light” Grant EP/J01771X/1. Quantum dots are of growing interest as emissive materials in light emitting devices. Here first we report the formation of highly luminescent organic capped colloidal cadmium sulfide (CdS) nanoparticles having the highest photoluminescence quantum yield of 69% in solutions and 34% in neat thin films in the near-infrared range. Second, we also show efficient electroluminescence in the near-infrared from solution processed hybrid light emitting diodes (LEDs) based on such colloidal CdS quantum dots embedded in an organic semiconductor matrix forming a nanocomposite active layer. We also discuss the device structure and role of the doped active layer in efficiency improvement. With optimized active layer thickness and concentration of QDs, the device exhibits an external electroluminescence quantum efficiency of 0.62% at a peak emission wavelength of 760 nm, providing a route to solution processable flexible light sources for biosensors and medicine. Publisher PDF

Nanostructured composites of inorganic and organic materials are attracting extensive interest for electronic and optoelectronic device applications. Here we report a novel method for the fabrication and patterning of metal selenide nanoparticles in organic semiconductor films that is compatible with solution processable large area device manufacturing. Our approach is based upon the controlled in situ decomposition of a cadmium selenide precursor complex in a film of the electron transporting material 1,3,5-tris(N-phenyl-benzimidazol-2-yl)-benzene (TPBI) by thermal and optical methods. In particular, we show that the photoluminescence quantum yield (PLQY) of the thermally converted CdSe quantum dots (QDs) in the TPBI film is up to 15%. We also show that laser illumination can form the QDs from the precursor. This is an important result as it enables direct laser patterning (DLP) of the QDs. DLP was performed on these nanocomposites using a picosecond laser. Confocal microscopy shows the formation of emissive QDs after laser irradiation. The optical and structural properties of the QDs were also analysed by means of UV-Vis, PL spectroscopy and transmission electron microscopy (TEM). The results show that the QDs are well distributed across the film and their emission can be tuned over a wide range by varying the temperature or irradiated laser power on the blend films. Our findings provide a route to the low cost patterning of hybrid electroluminescent devices. This journal is © The Royal Society of Chemistry.