Replies to post #32047 on Quantum Materials Corp. (fka QTMM)

[Jamis1]

Nice find, Chess! We all new those think shells were the holy grail of qdots! ;)

[chessmite]

excerpts from

Colloidal quantum dots (QDs) exhibit unique properties such as size-controllable color tunability by the quantum confinement effect, narrow emission linewidth and low-cost solution-based processing, which make QD a rising candidate material for optoelectronic device such as lasers, photodetectors, solar cells and light-emitting diodes (LEDs) [1–3]. Among these applications, colloidal QDs based LEDs (QD-LEDs) has been investigated popularly because it’s potential impacts to the display and lighting industry. Many research groups have attempted to enhance device performance using various QD compositions and device structures [4–6]. While the performance of QD-LEDs using II-VI semiconductor cadmium selenide (CdSe) colloidal QDs has been upgraded dramatically, a prominent future task is the substitution of Cd-containing QDs by less toxic materials. There have been only a few studies on QD-LEDs using Cd-free QDs [7–12]. Indium phosphide (InP) among III-V semiconductor nanocrystals is the most promising materials for Cd-free QD-LEDs owing to less ionic lattice, reduced toxicity and wide emission spectrum tunability covering the range of visible light [13–15]. The electroluminescent (EL) performance of QD-LEDs using InP QDs can be improved by the optimization of device structure and materials for the carrier balance in the multi-layered LED structure. However, the reported EL performance is insufficient and there are still many problems left such as EL quenching by Auger recombination, efficiency roll-off and device degradation, which limits the performance of QD-LEDs [16].
In this work, efficient Cd-free QD-LEDs were fabricated using InP/ZnSe/ZnS multishell QDs synthesized by the heating-up method [17]. The thicker ZnS shell of multishell QDs was adapted to improve the device efficiency, and the optoelectronic characteristics of QD-LEDs were investigated. Moreover, a serious QD charging problem was found in EL stability measurement, however it was also suppressed by the QD system of thicker ZnS shell to some extent.


The performance of our InP-based QD-LEDs can be matched to that of traditional Cd-based QD- LEDs, which shows the great potential for the Cd-free future information displays. With further investigation, the performance of InP-based QD-LEDs would be more improved by optimizing the core/multishell structure of QDs and charge balance in multi-layered system.


.......anyway one can get an inkling as to why InP/ZnS and why more research


Looking Forward

[Roth_IRA_3000]

Princeton creates a custom 3D printer that prints quantum dot LEDs from scratch.


http://www.extremetech.com/extreme/193583-princeton-creates-a-custom-3d-printer-that-prints-quantum-dot-leds-from-scratch

[chessmite]

for those that found #32047 (Increased shell thickness in indium phosphide multishell quantum dots leading to efficiency and stability enhancement in light-emitting diodes) interesting;


White lighting device from composite films embedded with hydrophilic Cu(In, Ga)S2/ZnS and hydrophobic InP/ZnS quantum dots
2014

Two types of non-Cd quantum dots (QDs)—In/Ga ratio-varied, green-to-greenish-yellow fluorescence-tuned Cu-In-Ga-S (CIGS) alloy ones, and red-emitting InP ones—are synthesized for use as down-converters in conjunction with a blue light-emitting diode (LED). Among a series of Ga-rich CI1-xGxS/ZnS core/shell QDs (x = 0.7, 0.8, and 0.9), CI0.2G0.8S/ZnS QD is chosen for the hydrophobic-to-hydrophilic surface modification via an in-situ ligand exchange and then embedded in a water-soluble polyvinyl alcohol (PVA). This free-standing composite film is utilized as a down-converter for the fabrication of a remote-type white QD-LED, but the resulting bi-colored device exhibits a cool white light with a limited color rendering index property. To improve white light qualities, another QD-polymer film of hydrophobic red InP/ZnS QD-embedding polyvinylpyrrolidone is sequentially stacked onto the CI0.2G0.8S/ZnS QD-PVA film, producing a unique dual color-emitting, flexible and transparent bilayered composite film. Tri-colored white QD-LED integrated with the bilayered QD film possesses an exceptional color rendering property through reinforcing a red spectral component and balancing a white spectral distribution.
http://iopscience.iop.org/0957-4484/25/22/225601




InP/ZnSe/ZnS: A Novel Multishell System for InP Quantum Dots for Improved Luminescence Efficiency and Its application in a Light-Emitting Device
2012

Indium phosphide (InP) quantum dots (QDs) are considered alternatives to Cd-containing QDs for application in light-emitting devices. The multishell coating with ZnSe/ZnS was shown to improve the photoluminescence quantum yield (QY) of InP QDs more strongly than the conventional ZnS shell coating. Structural proof for this system was provided by X-ray diffraction and transmission electron microscopy. QY values in the range of 50–70% along with peak widths of 45–50 nm can be routinely achieved, making the optical performance of InP/ZnSe/ZnS QDs comparable to that of Cd-based QDs. The fabrication of a working electroluminescent light-emitting device employing the reported material demonstrated the feasibility of the desired application.
http://www.tandfonline.com/doi/abs/10.1080/15980316.2012.683537#.VF-GJ5Ao5jo



Remote-type, high-color gamut white light- emitting diode based on InP quantum dot color converters
2014

Sun-Hyoung Lee,1 Ki-Heon Lee,1 Jung-Ho Jo,1 Byoungnam Park,1 Yongwoo Kwon,1 Ho Seong Jang,2 and Heesun Yang,1,* 1 Department of Materials Science and Engineering, Hongik University, Seoul 121-791, South Korea 2 Center for Materials Architecturing, Korea Institute of Science and Technology, Seoul 136-791, South Korea *[e-mail]
Abstract: This work reported on synthesis of highly efficient, color-pure green- and red-emitting non-Cd InP/ZnS core/shell quantum dots (QDs) and their utilization as color converters for the fabrication of display backlighting QD-based white light-emitting diode (LED). Green and red QD emitters were first individually embedded into a transparent polymeric matrix of polyvinylpyrrolidone and the resulting two free-standing QD composite plates were then physically combined into a bilayered form. White QD-LED was fabricated by remotely loading the bilayered QD plate of a red-on-green configuration onto blue LED chip. This remote-type white device generated a spectrally well-resolved, tricolored electroluminescent spectrum, and exhibited luminous efficacies of 8.9-16.7 lm/W, depending on forward currents of 20-100 mA, and a high color gamut of 87%. ©2014 Optical Society of America

Quantum dot-light-emitting diode (QD-LED), where visible-fluorescent QDs as color converters are integrated with an LED chip as an excitation source, has been intensively investigated for last decade. Bi- or tricolored white light emission can be typically generated through the combination of the blue emission transmitted from a chip plus the QD emission(s) color-converted by the blue excitation. The primary QD compositional candidates for LED fabrication may be categorized into Cd-containing II-VI group [1–4] versus non-Cd III-V (e.g., InP [5–7]) and I-III-VI ones (e.g., ternary Cu-In-S (CIS) [8–11] and its quaternary derivatives such as Cu-In-Ga-S [12] and Zn-Cu-In-S [13,14]). Depending on the spectral position, coverage, and ratio of QD emissions in white QD-LEDs, the resulting white lights possess different figure-of-merits such as color rendering index (CRI) and color gamut, which are key metrics in general lighting and display backlighting sources, respectively. Using Cd- containing QDs high-quality white lights with a color gamut as wide as 104% relative to the National Television Systems Committee (NTSC) color space [1] as well as a CRI close to 90 [2] have been already demonstrated through wisely designing the white spectral distribution. On the other hand, the work on non-Cd QDs-integrated white LEDs has been exclusively targeted toward the fabrication of general lighting devices [5–14]. This is mainly because the emission bandwidths of non-Cd QDs available to date are quite broader, i.e., less color-pure, compared to Cd-containing rivals. Herein, highly fluorescent, color-pure green and red non- Cd QDs of InP/ZnS core/shell (C/S) are synthesized, embedded into a transparent polymer matrix to prepare free-standing QD-polymer composites, and then for the first time utilized as color converters for the fabrication of remote-type, high-color gamut white QD-LED.
http://www.opticsinfobase.org/view_article.cfm?gotourl=http%3A%2F%2Fwww%2Eopticsinfobase%2Eorg%2FDirectPDFAccess%2FD3B82B48%2DBF0B%2D6A89%2D3211395C6C215D0B%5F289529%2Fome%2D4%2D7%2D1297%2Epdf%3Fda%3D1%26id%3D289529%26seq%3D0%26mobile%3Dno&org=

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....and to think QMC can do HMF and is adding staff to work on InP/ZnS

Know what you own, stick to your facts, and trade your way.

Standing By and Looking Forward here.

GLTA