Carrier Relaxation Dynamics in Lead Sulfide Colloidal Quantum Dots

Istrate, Emanuel; Hoogland, Sjoerd; Sukhovatkin, Vlad; Levina, Larissa; Myrskog, Stefan; Smith, P. W.; Sargent, Edward H.

doi:10.1021/jp076809g

Cited by 43 publications

(51 citation statements)

References 22 publications

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“…On the other hand the sublinear behavior observed is indicative of the presence of non-linear exciton effects. At the pump fl uencies used in our study, it has been found that Auger recombination is the dominant recombination mechanism in PbS QDs [ 28 ] if more than one exciton is excited per dot. It can be observed ( Table 2 ) that samples showing large PL quenching ratios or equivalently weak emission i.e.…”

Section: Photoluminescencementioning

confidence: 74%

Optical Properties of Organic Semiconductor Blends with Near‐Infrared Quantum‐Dot Sensitizers for Light Harvesting Applications

Itskos

Othonos

Rauch

et al. 2011

Advanced Energy Materials

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techniques at large area substrates. A common confi guration of such devices is based on binary organic bulk heterojunctions of a conjugated polymer acting as electron donor and a fullerene material acting as electron acceptor. Absorption of light generates excitons that encounter the donor-acceptor heterointerface and dissociate. Exciton dissociation is followed by electron transfer from the polymer to the fullerene that leads to generation of photocurrent. Solar cell devices based on such bulk heterojunctions have recently shown promising results including power conversion effi ciencies in the range of 6-7.5% [ 1 , 2 ] , lifetime of over 1 year under real environmental conditions [ 3 ] and proven proof of concept for high throughput fabrication using printing [ 4 , 5 ] and spray coating technologies [ 5 ] .However a signifi cant limitation on the effi ciency of such devices is that absorption by the blends is mainly limited to visible wavelengths so that a signifi cant fraction of the solar emission energy, occurring at longer wavelengths, cannot be harvested. To circumvent this limitation, parallel to research for low bandgap polymer materials [ 6 , 7 ] a signifi cant effort has been carried out on the incorporation of red and infrared-absorbing colloidal nanocrystals in bulk hetero junction organic based blends. The main idea, introduced by Alivisatos and coworkers [ 8 ] Optical Properties of Organic Semiconductor Blends with Near-Infrared Quantum-Dot Sensitizers for Light Harvesting ApplicationsWe report an optical investigation of conjugated polymer (P3HT)/fullerene (PCBM) semiconductor blends sensitized by near-infrared absorbing quantum dots (PbS QDs). A systematic series of samples that include pristine, binary and ternary blends of the materials are studied using steadystate absorption, photoluminescence (PL) and ultrafast transient absorption. Measurements show an enhancement of the absorption strength in the near-infrared upon QD incorporation. PL quenching of the polymer and the QD exciton emission is observed and predominantly attributed to intermaterial photoinduced charge transfer processes. Pump-probe experiments show photo-excitations to relax via an initial ultrafast decay while longer-lived photoinduced absorption is attributed to charge transfer exciton formation and found to depend on the relative ratio of QDs to P3HT:PCBM content. PL experiments and transient absorption measurements indicate that interfacial charge transfer processes occur more effi ciently at the fullerene/polymer and fullerene/nanocrystal interfaces compared to polymer/nanocrystal interfaces. Thus the inclusion of the fullerene seems to facilitate exciton dissociation in such blends. The study discusses important and rather unexplored aspects of exciton recombination and charge transfer processes in ternary blend composites of organic semiconductors and near-infrared quantum dots for applications in solution-processed photodetectors and solar cells.

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Section: Photoluminescencementioning

confidence: 74%

Optical Properties of Organic Semiconductor Blends with Near‐Infrared Quantum‐Dot Sensitizers for Light Harvesting Applications

Itskos

Othonos

Rauch

et al. 2011

Advanced Energy Materials

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“…28 These dynamics reflect physical processes which are important, beyond fundamental interest, for applications in, e.g., photovoltaics and optoelectronics. [15][16][17][18][21][22][23][24][25][26][27]51,52 In Fig. 6, the dependence of the FWM amplitude on 23 is shown on 4.4 nm PbS CQDs for two excitation wavelengths, either resonant with the excitonic ground state ͑upper curves͒ or closer to the first excited state ͑lower curve͒.…”

Section: B Dynamicsmentioning

confidence: 99%

“…With the focus on measuring carrier multiplication [15][16][17][18][21][22][23] and Auger recombination, [24][25][26][27] many recent experiments on carrier dynamics in PbX CQDs have been based on resolving the transient absorption bleaching of the excitonic ground-state transition after pulsed excitation at high photon energies. From these nonresonant pump-probe experiments, it is however difficult to extract the dynamics of the ground-state exciton only since many pathways come into play over similar time scales including carrier relaxation, photoionization, Auger recombination, and exciton redistribution between different energy states.…”

Section: Introductionmentioning

confidence: 99%

Four-wave-mixing imaging and carrier dynamics of PbS colloidal quantum dots

et al. 2010

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We demonstrate coherent multiphoton imaging of PbS colloidal quantum dots based on the detection of their transient resonant four-wave-mixing ͑FWM͒ emission under 150 fs pulsed laser excitation. Background-free imaging of PbS quantum dots in resonance with their ground-state excitonic absorption at 1.2 m wavelength is shown, with intrinsic optical sectioning and a spatial resolution better than the one-photon diffraction limit, promising for deep tissue microscopy. The four-wave-mixing efficiency is found to be resonant to the groundstate absorption maximum, which is a prerequisite for spectral multiplexing. The measured FWM dynamics is consistent with the presence of charged exciton and biexiton Auger recombination in the 10-100 ps time scale, phonon-assisted exciton thermalization in the nanosecond time scale, and excitonic recombination in the microsecond time scale.

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“…The timescale of Auger processes is typically on the order of 1–100 ps in single component NCs such as PbSe [199], Si [173], PbS [202], CdTe [203], Ge [204], InAs [205], or Pb-perovskites [161]. The Auger timescales in NCs are faster than those in the corresponding bulk material [204].…”

Section: Excited-state Dynamics In Semiconductor Nanocrystalsmentioning

confidence: 99%

Excited-State Dynamics in Colloidal Semiconductor Nanocrystals

Rabouw

Donegá

2016

Top Curr Chem (Z)

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Colloidal semiconductor nanocrystals have attracted continuous worldwide interest over the last three decades owing to their remarkable and unique size- and shape-, dependent properties. The colloidal nature of these nanomaterials allows one to take full advantage of nanoscale effects to tailor their optoelectronic and physical–chemical properties, yielding materials that combine size-, shape-, and composition-dependent properties with easy surface manipulation and solution processing. These features have turned the study of colloidal semiconductor nanocrystals into a dynamic and multidisciplinary research field, with fascinating fundamental challenges and dazzling application prospects. This review focuses on the excited-state dynamics in these intriguing nanomaterials, covering a range of different relaxation mechanisms that span over 15 orders of magnitude, from a few femtoseconds to a few seconds after photoexcitation. In addition to reviewing the state of the art and highlighting the essential concepts in the field, we also discuss the relevance of the different relaxation processes to a number of potential applications, such as photovoltaics and LEDs. The fundamental physical and chemical principles needed to control and understand the properties of colloidal semiconductor nanocrystals are also addressed.

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Carrier Relaxation Dynamics in Lead Sulfide Colloidal Quantum Dots

Cited by 43 publications

References 22 publications

Optical Properties of Organic Semiconductor Blends with Near‐Infrared Quantum‐Dot Sensitizers for Light Harvesting Applications

Optical Properties of Organic Semiconductor Blends with Near‐Infrared Quantum‐Dot Sensitizers for Light Harvesting Applications

Four-wave-mixing imaging and carrier dynamics of PbS colloidal quantum dots

Excited-State Dynamics in Colloidal Semiconductor Nanocrystals

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