Low Threshold, Amplified Spontaneous Emission from Core‐Seeded Semiconductor Nanotetrapods Incorporated into a Sol–Gel Matrix

Liao, Yi-Le; Xing, Guichuan; Mishra, Nimai; Sum, Tze Chien; Chan, Yinthai

doi:10.1002/adma.201200121

Cited by 45 publications

(67 citation statements)

References 29 publications

(30 reference statements)

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“…13 With all of these aforementioned promises, in the nanocrystal lasing context, CdSe/CdS NRs have become one of the most heavily studied materials systems. 18,24 Recently, singlemode, single-exciton and tunable laser emission on a silica microsphere 25 and low-threshold amplied spontaneous emission (ASE) and lasing with two-photon pumping mechanism 10 have been successfully demonstrated with CdSe/CdS core/shell NRs. Moreover, it was shown that nearly temperature-independent ASE can be possible with CdSe/CdS core/shell NRs 26 and controllable transition of the ASE peak from the CdSe core region to the CdS shell region can be nely tuned by changing the length of the nanorod and the excitation intensity.…”

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confidence: 99%

Type-tunable amplified spontaneous emission from core-seeded CdSe/CdS nanorods controlled by exciton–exciton interaction

et al. 2014

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Type-tunable optical gain performance of core-seeded CdSe/CdS nanorods is studied via two-photon optical pumping. Controlling the Colloidal semiconductor nanocrystals have recently arisen as promising candidates to be utilized as active gain media for lasing applications. 1,2 With their band gap tunability (via size and shape modications), efficient band edge emission (even at room temperature), discrete band structure, and synthesis through facile wet-chemistry, it is possible to achieve colortunable, low-threshold, temperature insensitive and solution processed lasers from colloidal quantum dots (CQDs). [2][3][4][5][6] However, there are various problems and challenges associated with CQD-based lasers. One way of achieving stimulated emission from the CQDs is through multi-exciton generation. When multiple excitons are formed, the Auger recombination (AR) process becomes more pronounced and inhibits optical gain in CQDs. [7][8][9] In addition, high intensity optical pumping, which is required for stimulated emission, can photo-damage the sample and decrease the stability. 10 To address these issues, CQDs having suppressed AR and exhibiting a higher absorption cross-section, which can increase the stability of CQDs by lowering the optical gain threshold, are strongly required.As a subclass of nanocrystals, core/shell nanorods (NRs) have been extensively considered for lasing applications and optical gain studies to overcome these problems with possibility of engineering their electronic structure for longer gain lifetime and increased absorption cross-section. 11-14 From different varieties of core/shell NRs, core-seeded CdSe/CdS NRs have become quite attractive. With advances in the colloidal synthesis of CdSe/CdS core/shell NRs, it is possible to synthesize highly efficient and crystalline CdSe/CdS core/shell NRs having a narrow size distribution by nely controlling their shape and size. 15,16 Furthermore, due to shallow band offset for electrons in the CdSe/CdS core/shell material system, a partial separation of electron and hole wavefunctions is observed which is known as the quasi type-II electronic structure that contributes to the suppression of Auger recombination, which is highly critical for achieving lasing. 11,[16][17][18] The other advantage of having a lower energy barrier for electrons in CdSe/CdS NRs is that, by simply changing their core and shell sizes, it is possible to tailor the electron and hole wavefunction overlap and tune CdSe/CdS NRs from type-I-like to quasi-type-II-like band alignment, which can be an important design consideration when engineering the gain/loss mechanisms in practical lasing systems. [19][20][21][22][23] Moreover, due to the narrower band gap of CdS with respect to ZnS, the absorption cross-section of CdSe/CdS core/shell NRs is greatly enhanced. 13 With all of these aforementioned promises, in the nanocrystal lasing context, CdSe/CdS NRs have become one of the most heavily studied materials systems. 18,24 Recently, singlemode, single-exciton and tunable laser emis...

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Type-tunable amplified spontaneous emission from core-seeded CdSe/CdS nanorods controlled by exciton–exciton interaction

et al. 2014

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“…We employed the seeded growth approach of Fiore et al 18. with modified surfactant chemistry for enhanced monodispersity21920. The resulting tetrapods were as follows: thin/short (TP1: 6.3 nm±0.5 nm/24.8 nm±2.3 nm), thick/short (TP2: 10.9 nm±0.8 nm/27.6 nm±2.9 nm), thin/long (TP3: 8.2 nm±1.3 nm/40.7 nm±3.8 nm) and thick/long (TP4: 10.6 nm±2.4 nm/41.3 nm±4.6 nm) (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…CdSe/CdS core/arm tetrapods have been investigated for their unusual characteristics of ultra-large absorption cross-section1, long biexciton lifetimes2 and strain-dependent emission3. These traits render such quantum dot (QD)-‘seeded' tetrapods potentially useful as efficient energy-conversion materials for solar-cell applications1 or as low-threshhold gain media for lasing applications2, respectively.…”

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Using shape to turn off blinking for two-colour multiexciton emission in CdSe/CdS tetrapods

et al. 2017

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Semiconductor nanostructures capable of emitting from two excited states and thereby of producing two photoluminescence colours are of fundamental and potential technological significance. In this limited class of nanocrystals, CdSe/CdS core/arm tetrapods exhibit the unusual trait of two-colour (red and green) multiexcitonic emission, with green emission from the CdS arms emerging only at high excitation fluences. Here we show that by synthetic shape-tuning, both this multi-colour emission process, and blinking and photobleaching behaviours of single tetrapods can be controlled. Specifically, we find that the properties of dual emission and single-nanostructure photostability depend on different structural parameters—arm length and arm diameter, respectively—but that both properties can be realized in the same nanostructure. Furthermore, based on results of correlated photoluminescence and transient absorption measurements, we conclude that hole-trap filling in the arms and partial state-filling in the core are necessary preconditions for the observation of multiexciton multi-colour emission.

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“…Therefore, CQDs having suppressed AR are strongly required for achieving high quality CQD-based lasers. To address this issue, CQDs having different size, shape and electronic structure have been synthesized and studied extensively [3][4][5]. Generally, suppression of AR and lower optical gain thresholds are achieved via reducing the wavefunction overlap of the electron and hole in a CQD.…”

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Low-threshold optical gain and lasing of colloidal nanoplatelets

Keleştemur

Güzeltürk

Olutaş

et al. 2014

2014 IEEE Photonics Conference

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Semiconductor nanocrystals, which are also known as colloidal quantum dots (CQDs), are highly attractive materials for high performance optoelectronic device applications such as lasers. With their size, shape and composition tunable electronic structure and optical properties, CQDs are highly desired for achieving full-color, temperature-insensitive, low-threshold and solution-processed lasers [1,2]. However, due to their small size, they suffer from the nonradiative multiexciton Auger Recombination (AR), where energy of a bound electronhole pair is transferred to a third particle of either an electron or a hole instead of radiative recombination. Therefore, CQDs having suppressed AR are strongly required for achieving high quality CQD-based lasers. To address this issue, CQDs having different size, shape and electronic structure have been synthesized and studied extensively [3][4][5]. Generally, suppression of AR and lower optical gain thresholds are achieved via reducing the wavefunction overlap of the electron and hole in a CQD. However, the separation of the electron and hole wavefunctions will dramatically decrease the oscillator strength and optical gain coefficient, which is highly critical for achieving high performance lasers. Therefore, colloidal materials with suppressed AR and high gain coefficients are highly welcomed. Here, we study optical gain performance of colloidal quantum wells [6] of CdSe-core and CdSe/CdS core/crown nanoplatelets (NPLs) that demonstrate remarkable optical properties with ultra-low threshold one-and two-photon optical pumping. As a result of their giant oscillator strength, superior optical gain and lasing performance are achieved from these colloidal NPLs with greatly enhanced gain coefficient [7].

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Low Threshold, Amplified Spontaneous Emission from Core‐Seeded Semiconductor Nanotetrapods Incorporated into a Sol–Gel Matrix

Cited by 45 publications

References 29 publications

Type-tunable amplified spontaneous emission from core-seeded CdSe/CdS nanorods controlled by exciton–exciton interaction

Type-tunable amplified spontaneous emission from core-seeded CdSe/CdS nanorods controlled by exciton–exciton interaction

Using shape to turn off blinking for two-colour multiexciton emission in CdSe/CdS tetrapods

Low-threshold optical gain and lasing of colloidal nanoplatelets

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