Exciton–Exciton Interaction and Optical Gain in Colloidal CdSe/CdS Dot/Rod Nanocrystals

Saba, Michele; Minniberger, Stefan; Quochi, Francesco; Roither, J.; Marceddu, Marco; Gocalinska, Agnieszka; Kovalenko, Maksym V.; Talapin, Dmitri V.; Heiß, Wolfgang; Mura, Andrea; Bongiovanni, Giovanni

doi:10.1002/adma.200901482

Cited by 86 publications

(98 citation statements)

References 23 publications

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“…The smaller mismatch between the core and the shell in these nanostructures resulted in a better passivation and a reduction of non radiative losses. In addition, CdSe/CdS QRs acted as quasi type II nanostructure because the holes were confined in the CdSe core while electrons were strongly delocalized in the ellipsoidal CdS shell [40][41][42]. Consequently, Auger recombination was significantly decreased, and ASE threshold was reduced down to 0.1 mJ/cm 2 .…”

Section: Colloidal Quantum Rodsmentioning

confidence: 82%

“…Such a dot in rod structures not only provides an enhancement in the quantum yield, but also another degree of freedom to tune the band-gap. Indeed, energy 30001-p6 I. Suárez Alvarez: Active photonic devices based on colloidal semiconductor nanocrystals and organometallic halide perovskites position of the absorption and emission exciton peaks can be tuned independently by using the dimensions of the shell and the core respectively [40][41][42]. As a consequence, it became possible to minimize self-absorption losses by enlarging the Stokes shift between the absorption and the PL, and hence to reduce the stimulated emission threshold.…”

Section: Colloidal Quantum Rodsmentioning

confidence: 99%

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Active photonic devices based on colloidal semiconductor nanocrystals and organometallic halide perovskites

Suárez¹

2016

Eur. Phys. J. Appl. Phys.

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Abstract. Semiconductor nanocrystals have arisen as outstanding materials to develop a new generation of optoelectronic devices. Their fabrication under simple and low cost colloidal chemistry methods results in cheap nanostructures able to provide a wide range of optical functionalities. Their attractive optical properties include a high absorption cross section below the band gap, a high quantum yield emission at room temperature, or the capability of tuning the band-gap with the size or the base material. In addition, their solution process nature enables an easy integration on several substrates and photonic structures. As a consequence, these nanoparticles have been extensively proposed to develop several photonic applications, such as detection of light, optical gain, generation of light or sensing. This manuscript reviews the great effort undertaken by the scientific community to construct active photonic devices based on these nanoparticles. The conditions to demonstrate stimulated emission are carefully studied by comparing the dependence of the optical properties of the nanocrystals with their size, shape and composition. In addition, this paper describes the design of different photonic architectures (waveguides and cavities) to enhance the generation of photoluminescence, and hence to reduce the threshold of optical gain. Finally, semiconductor nanocrystals are compared to organometallic halide perovskites, as this novel material has emerged as an alternative to colloidal nanoparticles.

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Section: Colloidal Quantum Rodsmentioning

confidence: 82%

Section: Colloidal Quantum Rodsmentioning

confidence: 99%

Active photonic devices based on colloidal semiconductor nanocrystals and organometallic halide perovskites

Suárez¹

2016

Eur. Phys. J. Appl. Phys.

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“…[ 19 ] Figure 1 (d) shows the dependence of I th as a function of the pump wavelength (sample S03). A strong reduction of I th for off-resonant pumping is observed.…”

Section: Doi: 101002/adma201202067mentioning

confidence: 99%

Nearly Temperature‐Independent Threshold for Amplified Spontaneous Emission in Colloidal CdSe/CdS Quantum Dot‐in‐Rods

Moreels¹,

Rainò²,

Gomes³

et al. 2012

Advanced Materials

107

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By careful engineering of the core and shell dimensions in CdSe/CdS colloidal hetero‐nanocrystals, amplified spontaneous emission can be triggered from either the core, shell, or both states simultaneously. The ASE threshold is almost constant over a temperature interval of 5–325 K. This feature is unique to quantum dots and highlights their potential as a gain material, suitable for lasing at elevated temperatures.

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“…21 In addition, the tunability of electron and hole wavefunction overlap in this materials system has also been discussed in the literature for both entangled photon generation 27 and nanocrystal lasing applications. 20 However, to the best of our knowledge, controlled shiing of the ASE peak with respect to the spontaneous emission in CdSe/CdS NRs through systematically changing the electronic property of the NRs has not been demonstrated. Here, as a result of the exciton-exciton interaction engineering via adjusting the core and the shell size, we show the electronic type tunability of the NR feature resulting in blue-shiing (type-II-like), and red-shiing (type-Ilike) ASE with respect to the spontaneous emission of NRs pumped with the two-photon absorption (TPA) optical pumping mechanism.…”

mentioning

confidence: 91%

“…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.…”

mentioning

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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Exciton–Exciton Interaction and Optical Gain in Colloidal CdSe/CdS Dot/Rod Nanocrystals

Cited by 86 publications

References 23 publications

Active photonic devices based on colloidal semiconductor nanocrystals and organometallic halide perovskites

Active photonic devices based on colloidal semiconductor nanocrystals and organometallic halide perovskites

Nearly Temperature‐Independent Threshold for Amplified Spontaneous Emission in Colloidal CdSe/CdS Quantum Dot‐in‐Rods

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

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