Recombination dynamics in CdTe/CdSe type-II quantum dots

Wang, Chun Hsiung; Chen, Tzung Te; Chen, Yang‐Fang; Ho, Mei Lin; Lai, Chih‐Wei; Chou, Pi‐Tai

doi:10.1088/0957-4484/19/11/115702

Cited by 35 publications

(27 citation statements)

References 36 publications

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“…The reduction in lifetime is attributed to the decrease in QD size in the low-speed printing, which has been reported previously. 31,32 In the smaller QD, a higher degree of overlap between the electron and hole wave functions leads to faster electron–hole recombination and thus a shorter lifetime. 33 …”

Section: Resultsmentioning

confidence: 99%

Patterning and fluorescence tuning of quantum dots with haptic-interfaced bubble printing

et al. 2017

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Semiconductor quantum dots (QDs) are attractive for a wide range of applications such as displays, light-emitting devices, and sensors due to their properties such as tunable fluorescence wavelength, high brightness, and narrow bandwidth. Most of the applications require precise patterning of QDs with targeted properties on solid-state substrates. Herein, we have developed a haptic-interfaced bubble printing (HIBP) technique to enable high-resolution (510 nm) high-throughput (>104 μm s−1) patterning of QDs with strong emission tunability and to significantly enhance the accessibility of the technique via a smartphone device. The scalability and versatility of the HIBP are demonstrated in our arbitrary patterning of QDs on plasmonic substrates. A detailed study of plasmonic and photothermal interactions is performed via programmed stage movements to realize tunability of the emission wavelength and lifetime. Finally, the influence of the hand movement on the properties of the printed QDs in terms of emission wavelength tuning from yellow to blue is established. This work provides a single-step macroscale platform to manipulate nanoscale properties at high resolution and high throughput.

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Section: Resultsmentioning

confidence: 99%

Patterning and fluorescence tuning of quantum dots with haptic-interfaced bubble printing

et al. 2017

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“…This is in accordance with literature data. 48 Most important, however, is that the slopes are almost the same at the two temperatures. This illustrates that no additional relaxation mechanisms (i.e., only the approximately microsecond spontaneous emission) become effective during the whole temperature range.…”

Section: B Spontaneous Emission At Low Excitation Densitiesmentioning

confidence: 95%

Spontaneous and stimulated emission dynamics of PbS quantum dots in a glass matrix

2013

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Optical properties and relaxation mechanisms of PbS quantum dots in glass matrix (PbS:Glass) have been systematically investigated by transmission and (steady-state and transient) photoluminescence spectroscopy. Key parameters are determined by combining the data with semiempirical expressions, based on which the recombination mechanisms including spontaneous and stimulated emissions have been discussed as a function of temperature by referring to a multilevel model including intrinsic (or band-to-band transition), bright, dark, and ground states. The results disclose that (i) the existence of a dark exciton state is the main reason for thermal quenching of the emission even at low temperatures due to the strong multiacoustic phonon coupling, (ii) the "intrinsic" spontaneous emission related to the intrinsic state is observed with an approximately nanosecond lifetime, in contrast to the "regular" spontaneous emission from the bright exciton state with an approximately microsecond lifetime, and (iii) stimulated emission, which has a lifetime of 20-40 ps and shows power-dependence of excitation density (or temperature), only appears from the intrinsic state but not the (bright) exciton state when enough accumulation of photogenerated carriers is reached. Furthermore, we find that the thermal conductivity will become crucial for future PbS:Glass related optoelectronic device applications.

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“…The temperature dependence of the PL bandwidth of our CdTe/CdSe (C/S) type-II QDs was quite different from those observed in previous reports. In one previous study, CdTe/CdSe (C/S) QDs (average core radius 3.45 nm, average shell thickness 0.9 nm) QDs, fwhm first increased and later decreased as T was raised from 15 to 300 K; the change of direction occurred at 200 K. 19 The authors argued that the thermal broadening mostly contributed at low T and that the effect of carrier accumulation effect began at high T. Interestingly, the same group later reported similar experiments where the fwhm of CdTe/CdSe (2.7 nm average core radius/1.0 nm average shell thickness) QDs showed the monotonously increased PL fwhm as the elevating T. 20 The PL bandwidth of a QD sample is determined by the convolution of inhomogeneous broadening due to the size and shape distributions, and by homogeneous broadening that originates from the scattering of excitons by LO phonons and by acoustic phonons. Due to the phonon effect, the PL bandwidth is expected to broaden in bulk semiconductors and also in QDs.…”

Section: I(t) )mentioning

confidence: 97%

Unique Temperature Dependence and Blinking Behavior of CdTe/CdSe (Core/Shell) Type-II Quantum Dots

et al. 2010

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Temperature dependent photoluminescence (PL) spectroscopy in a range of 5 K to room temperature (RT, 290 K) and single dot blinking behavior were investigated for CdTe/CdSe (core/shell, C/S) quantum dots (QDs). The QDs show type-II characteristics as both of the valence and conduction band levels of the CdTe core are placed higher in energy than those of the CdSe shell. The thickness of the CdSe shell was varied to control the degree of type-II character, and bare CdTe QDs were used as controls. The CdTe/CdSe (C/S) QDs have unique PL properties including (i) high susceptibility to PL thermal quenching with an exciton dissociation energy as small as 18 meV, compared with 46 meV for the CdTe QD, (ii) smaller band gap change showing only half the reduction of the control within the temperature change, and (iii) up to 27% larger PL bandwidth broadening than the control. The unique temperature-dependent properties were enhanced as the type-II character was increased by the thicker CdSe shell. Single dot level PL intermittency characteristics were studied for quasi type-II CdTe/CdSe (C/S) QDs that have alloyed layers at the core-shell interface. The quasi type-II QDs exhibited more frequent PL intensity intermittence blinking on and off at 290 K when compared with the CdTe QDs. However, the blinking kinetics follows similar universal power law on/off probability distributions with the R on and R off exponents evaluated as 1.57 and 1.38, respectively.

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Recombination dynamics in CdTe/CdSe type-II quantum dots

Cited by 35 publications

References 36 publications

Patterning and fluorescence tuning of quantum dots with haptic-interfaced bubble printing

Patterning and fluorescence tuning of quantum dots with haptic-interfaced bubble printing

Spontaneous and stimulated emission dynamics of PbS quantum dots in a glass matrix

Unique Temperature Dependence and Blinking Behavior of CdTe/CdSe (Core/Shell) Type-II Quantum Dots

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