Efficient upconversion of photoluminescence via two-photon absorption in bulk and nanorod ZnO

Chen, Shula; Stehr, Jan Eric; Reddy, N. Koteeswara; Tu, C. W.; Chen, Weimin; Buyanova, Irina

doi:10.1007/s00340-012-5138-y

Cited by 26 publications

(25 citation statements)

References 33 publications

(42 reference statements)

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“…Resonant excitation 31 meV below the A:1s state at the trion energy for example [53], does not result in emission at the A:2s and B:1s energies in our experiment. Emission at higher energy than the laser can have several origins [54][55][56][57][58]65], here important information comes from the B-exciton emission: at 430 meV above the laser energy mechanisms purely based on phonon emission (i.e. laser cooling [66]) are very unlikely at the sample temperature T = 4 K. A more probable scenario is 2 photon absorption, made efficient by the A:1s as a real intermediate state.…”

Section: Resultsmentioning

confidence: 99%

Enabling valley selective exciton scattering in monolayer WSe2 through upconversion

Manca¹,

Glazov²,

Robert³

et al. 2017

Nat Commun

144

150

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Excitons, Coulomb bound electron–hole pairs, are composite bosons and their interactions in traditional semiconductors lead to condensation and light amplification. The much stronger Coulomb interaction in transition metal dichalcogenides such as WSe2 monolayers combined with the presence of the valley degree of freedom is expected to provide new opportunities for controlling excitonic effects. But so far the bosonic character of exciton scattering processes remains largely unexplored in these two-dimensional materials. Here we show that scattering between B-excitons and A-excitons preferably happens within the same valley in momentum space. This leads to power dependent, negative polarization of the hot B-exciton emission. We use a selective upconversion technique for efficient generation of B-excitons in the presence of resonantly excited A-excitons at lower energy; we also observe the excited A-excitons state 2s. Detuning of the continuous wave, low-power laser excitation outside the A-exciton resonance (with a full width at half maximum of 4 meV) results in vanishing upconversion signal.

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Section: Resultsmentioning

confidence: 99%

Enabling valley selective exciton scattering in monolayer WSe2 through upconversion

Manca¹,

Glazov²,

Robert³

et al. 2017

Nat Commun

144

150

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show abstract

“…Recently it was reported that ZnO can also exhibit efficient photon upconversion, that is, capable of converting two low‐energy photons into a single higher‐energy photon, which could open a window of opportunities for improved and even new device applications. Indeed energy upconversion currently attracts great attention in diverse research fields ranging from medicine and biology to optoelectronics and photonics .…”

Section: Introductionmentioning

confidence: 99%

“…Light upconversion in ZnO can proceed via several processes including two‐photon absorption (TPA) and two‐step two‐photon absorption (TS‐TPA) . In both processes excitation of carriers is accomplished by sequential absorption of two photons via an intermediate state.…”

Section: Introductionmentioning

confidence: 99%

“…TPA occurs via a virtual state and thus requires rather high excitation densities (i.e., of the order of P exc = 10 9 W cm −2 ) in spite of a lack of inversion symmetry adherent to the wurtzite crystal structure of this material. On the other hand, TS‐TPA can be achieved at remarkably low P exc ≈ 0.1 W cm −2 owing to the fact that the intermediate state involved in this process is a real state, for example, an energy level of a defect or impurity. This process therefore dominates in low excitation density regimes and has the benefit of relatively high (i.e., in the order of 1–2% at low P exc ) conversion efficiency without the need for intense excitation sources.…”

Section: Introductionmentioning

confidence: 99%

“…Such understanding, however, is currently lacking. The key questions, that is, what is the origin of the defect/impurity responsible for the TS‐TPA process in ZnO and the exact energy position of the corresponding intermediate state, remain unanswered, though we have most recently suggested that a native defect may be involved. The purpose of the present work is to reliably answer these questions based on comprehensive electron paramagnetic resonance (EPR) studies combined with detailed spectral dependent measurements of TS‐TPA.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Turning ZnO into an Efficient Energy Upconversion Material by Defect Engineering

Stehr

Chen

Reddy

et al. 2014

Adv Funct Materials

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Photon upconversion materials are attractive for a wide range of applications from medicine, biology to photonics. Among them, ZnO is of particular interest owing to its outstanding combination of materials and physical properties. Though energy upconversion has been demonstrated in ZnO, the exact physical mechanism is still unknown that prevents a control of the processes. Here, we show that defects formed in bulk and nanostructured ZnO synthesized using standard growth techniques play a key role in promoting efficient energy upconversion via two-step two-photon absorption (TS-TPA). From photoluminescence excitation of the anti-Stokes emissions, the threshold energy of the TS-TPA process is determined as being 2.10 -2.14 eV in all studied ZnO materials irrespective of the employed growth techniques. Our photo-electron paramagnetic resonance studies show that this threshold closely matches the ionization energy of the zinc vacancy -a common grown-in intrinsic defect in ZnO, thereby identifying the zinc vacancy as being the dominant defect responsible for the observed efficient energy upconversion. The upconversion is found to persist even at a low excitation density, making it attractive for photonic and photovoltaic applications.1

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Energy Upconversion in GaP/GaNP Core/Shell Nanowires for Enhanced Near‐Infrared Light Harvesting

Dobrovolsky

Sukrittanon

Kuang

et al. 2014

Small

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Semiconductor nanowires (NWs) have recently gained increasing interest due to their great potential for photovoltaics. A novel material system based on GaNP NWs is considered to be highly suitable for applications in efficient multi-junction and intermediate band solar cells.This work shows that though the bandgap energies of GaN x P 1-x alloys lie within the visible spectral range (i.e. within 540 -650 nm for the currently achievable x< 3%), coaxial GaNP NWs grown on Si substrates can also harvest infrared light utilizing energy upconversion.This energy upconversion can be monitored via anti-Stokes near-band-edge photoluminescence (PL) from GaNP, visible even from a single NW. The dominant process 2 responsible for this effect is identified as being due to two-step two-photon absorption (TS-TPA) via a deep level lying at about 1.28 eV above the valence band, based on the measured dependences of the anti-Stokes PL on excitation power and wavelength. The formation of the defect participating in the TS-TPA process is concluded to be promoted by nitrogen incorporation. The revealed defect-mediated TS-TPA process can boost efficiency of harvesting solar energy in GaNP NWs, beneficial for applications of this novel material system in third-generation photovoltaic devices.

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Efficient upconversion of photoluminescence via two-photon absorption in bulk and nanorod ZnO

Cited by 26 publications

References 33 publications

Enabling valley selective exciton scattering in monolayer WSe2 through upconversion

Enabling valley selective exciton scattering in monolayer WSe2 through upconversion

Turning ZnO into an Efficient Energy Upconversion Material by Defect Engineering

Energy Upconversion in GaP/GaNP Core/Shell Nanowires for Enhanced Near‐Infrared Light Harvesting

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