Bright infrared LEDs based on colloidal quantum-dots

Sun, Lixing; Choi, Joshua J.; Stachnik, David; Bartnik, Adam; Hyun, Byung‐Ryool; Malliaras, George G.; Hanrath, Tobias; Wise, Frank W.

doi:10.1557/opl.2013.382

Cited by 34 publications

(55 citation statements)

References 8 publications

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“…3a shows the dependence of the radiance spectra of the TGA based device with the increasing potential in the range comprised between 0 and +5 V. The electroluminescence spectra are situated at the same spectral position and present exactly the same shape than PL measurements, see ESI (Fig. 6 Devices with a surface area as large as 1.54 cm 2 have been prepared with just a 4-fold decrease of the EQE despite the area being enlarged 7 times, compared to Finally, the stability issues of the QD-LEDs have been analyzed. The results indicate that charge carriers are directly injected into the QD layer and undergo subsequent radiative recombination, thus avoiding the exciton generation on the polymer and subsequent energy transfer to the nanocrystals.…”

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confidence: 90%

“…3,6,13 Here we demonstrate the successful fabrication of NIR QD-LEDs using colloidal NIR emitting core-shell nanocrystals based on metal chalcogenides, which are constituted by a PbS core covered with a shell of CdS, a wider gap material, see Fig. 3,6,13 Here we demonstrate the successful fabrication of NIR QD-LEDs using colloidal NIR emitting core-shell nanocrystals based on metal chalcogenides, which are constituted by a PbS core covered with a shell of CdS, a wider gap material, see Fig.…”

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confidence: 99%

“…It is observed that the Stoke's shi, i.e. 6 Shorter hydrocarbon chains give rise to higher current densities. [29][30][31] This observation, together with the larger inter-dot interaction aer the growth of the QD lm, is consistent with red-shi of the emission spectra of QDs (Dl em z 30 nm) aer the deposition using TGA as the linker, which may contribute to lower signicantly the light emissive properties of the QDs in the lm.…”

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confidence: 99%

“…[29][30][31] This observation, together with the larger inter-dot interaction aer the growth of the QD lm, is consistent with red-shi of the emission spectra of QDs (Dl em z 30 nm) aer the deposition using TGA as the linker, which may contribute to lower signicantly the light emissive properties of the QDs in the lm. 6 It worth mentioning that the EQEs obtained for the MPA based devices are similar to those reported in a previous work using also MPAligand PbS QDs and exploiting the direct device conguration on ITO substrates, see Fig. 3a shows the dependence of the radiance spectra of the TGA based device with the increasing potential in the range comprised between 0 and +5 V. The electroluminescence spectra are situated at the same spectral position and present exactly the same shape than PL measurements, see ESI (Fig.…”

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confidence: 99%

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All solution processed low turn-on voltage near infrared LEDs based on core–shell PbS–CdS quantum dots with inverted device structure

et al. 2014

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confidence: 99%

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All solution processed low turn-on voltage near infrared LEDs based on core–shell PbS–CdS quantum dots with inverted device structure

et al. 2014

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“…[7][8][9] Therefore, an accurate determination of the conduction band (CB) and valence band (VB) of the NCs is important and a prerequisite in rational design of the building blocks using the NCs. The energy levels of the NCs are acquirable by X-ray absorption, [10] photoelectron, [11][12][13][14] or scanning tunneling spectroscopy.…”

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Insights into the Energy Levels of Semiconductor Nanocrystals by a Dopant Approach

Zhang

Xie

et al. 2013

Angew Chem Int Ed

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The energy levels of semiconductor nanocrystals (NCs) are among the key factors controlling the performance of solar cells [1][2][3][4][5][6] and optoelectronics devices. [7][8][9] Therefore, an accurate determination of the conduction band (CB) and valence band (VB) of the NCs is important and a prerequisite in rational design of the building blocks using the NCs. The energy levels of the NCs are acquirable by X-ray absorption, [10] photoelectron, [11][12][13][14] or scanning tunneling spectroscopy.[15] Theoretical predictions on band structures of the NCs have also been reported. [16][17][18][19][20] Recently, cyclic voltammetry (CV) [21][22][23] has been employed to estimate the CB and VB positions of the NCs. These techniques for determining the energy levels of the NCs generally involve sophisticated instruments and tedious sample preparation and/or complicated operation procedures. For example, the CV method requires that the samples are stable during the measurements. Furthermore, these methods depend on charging the NCs during the measurements, which may lead to a shift in their CB and/or VB positions. Thus, determination of the energy band positions of the NCs still remains a challenge.Herein, we developed an approach to determine the energy levels of the NCs by introduction of certain transitionmetal ions (dopants) into the NCs. It is well-known that the energy level of a dopant is independent on size of the host semiconductor. [24][25][26][27][28][29] If the energy level of the doped transition metal ions located in the energy gap of the host semiconductor NCs, band-gap photoluminescence (PL) of the NCs will usually be quenched. [24,26,29] Instead, a PL peak associated with the doped metal ions (Doping PL) appears. As shown in Scheme 1, bottom of the CB (or LUMO) of the NCs can thus be determined based on the doping PL, given the known position of the energy level of the dopant. The band gap (or HOMO-LUMO energy gap) of the NCs can be readily measured by using UV/Vis spectroscopy. Subsequently, the top of the VB (or HOMO) of the NCs is deducible by subtracting the band gap (or HOMO-LUMO energy gap) of the NCs from the energy level of the CB (or LUMO) of the NCs (see Supporting Information for the detailed procedure to calculate the energy levels of a typical sample).InP NCs and Cu doped InP NCs were used as a model system for determination of the energy levels of the NCs. InP NCs with various sizes and a relatively narrow size distribution [30] and Cu-doped InP NCs possessing an efficient doping PL [26,31,32] were synthesized according to reported methods (see the Supporting Information for the detailed synthetic procedures of all of the NCs concerned in this work, and Figure S1 a for the absorption and doping PL spectra of the as-prepared InP and Cu-doped InP NCs).

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Graphene Doping Improved Device Performance of ZnMgO/PbS Colloidal Quantum Dot Photovoltaics

Gao

et al. 2016

Adv Funct Materials

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Lead sulfi de (PbS) colloidal quantum dots (CQDs) solar cells possess the advantages of absorption into the infrared, solution processing, and multiple exciton generation, making them very competitive as a low-cost photovoltaic alternative. Employing an n-i-p ZnO/tetrabutylammonium (TBAI)-PbS/ ethanedithiol (EDT)-PbS device confi guration, the present study reports a 9.0% photovoltaic device through ZnMgO electrode engineering and graphene doping. Sol-gel-derived Zn 0.9 Mg 0.1 O buffer layer shows better transparency and higher conduction band maximum than ZnO, and incorporation of graphene and chlorinated graphene oxide into the TBAI-PbS and EDT-PbS layer respectively boosts carrier collection, leading to device with signifi cantly enhanced open circuit voltage and short-circuit current density. It is believed that incorporation of graphene into PbS CQD fi lm as proposed here, and more generally nanosheets of other materials, would potentially open a simple and powerful avenue to overcome the carrier transport bottleneck of CQD optoelectronic device, thus pushing device performance to a new level.

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Bright infrared LEDs based on colloidal quantum-dots

Abstract: Record-brightness infrared LEDs based on colloidal quantum-dots have been achieved through control of the spacing between adjacent quantum-dots. By tuning the size of quantum-dots, the emission wavelengths can be tuned between 900nm and 1650nm.

Cited by 34 publications

References 8 publications

All solution processed low turn-on voltage near infrared LEDs based on core–shell PbS–CdS quantum dots with inverted device structure

All solution processed low turn-on voltage near infrared LEDs based on core–shell PbS–CdS quantum dots with inverted device structure

Insights into the Energy Levels of Semiconductor Nanocrystals by a Dopant Approach

Graphene Doping Improved Device Performance of ZnMgO/PbS Colloidal Quantum Dot Photovoltaics

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