On the nonradiative and radiative decay rates and a modified exponential energy gap law for 4<i>f</i>–4<i>f</i> transitions in rare-earth ions

Dijk, J. M. F. Van; Schuurmans, M. F. H.

doi:10.1063/1.445485

Cited by 435 publications

(184 citation statements)

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“…Empirically, multiphonon non-radiative transfer is a predominant process when energy is less than 5-6 cut-off phonon energy [26]. Following that empirical rule also known as gap law, a dominance of multiphonon relaxation process is predicted for all DE < 3900 cm À1 and 4880 cm À1 for anatase and rutile, respectively.…”

Section: Tiomentioning

confidence: 99%

UV to NIR photon conversion in Nd-doped rutile and anatase titanium dioxide films for silicon solar cell application

et al. 2012

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. (0 0 4) anatase. An UV to NIR photon conversion is evidenced in the films. Indeed, intense and wellresolved emission lines from Nd 3+ have been observed upon excitation above the TiO 2 bandgap at room temperature. The sensitised emission of Nd 3+ is found to be much efficient in rutile than in anatase structure. Low temperature photoluminescence measurements lead to fine resolved peaks corresponding to the Nd 3+ 4f transitions with different spectral characteristic according to the host matrix used. Photoluminescence dependence temperature evidences that the light emission from Nd 3+ in anatase-based films is probably influenced by the presence of self-trapped excitons or by orbital interaction. Mechanisms of sensitisation host to Nd 3+ are proposed for both matrixes. Finally, the Nd dopant concentration and the microstructure of TiO 2 rutile films are found to affect the photoluminescence emission intensity. Rutile film (2 0 0) oriented is the most adapted host matrix to sensitise 1 at.% Nd 3+ ions for an emission around 1064 nm making such Nd-doped layers interesting for photon conversion by down shifting process.

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Section: Tiomentioning

confidence: 99%

UV to NIR photon conversion in Nd-doped rutile and anatase titanium dioxide films for silicon solar cell application

et al. 2012

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“…A quenching mechanism for luminescent species characterized by a small parabola offset is multiphonon relaxation, where the energy gap is bridged by the simultaneous emission of phonons 8,34 (Figure 5b). The nonradiative multiphonon relaxation rate decreases exponentially with the number of phonons p (with p = ΔE/pω max , where ΔE is the energy gap and pω max is the maximum phonon energy).…”

Section: Articlementioning

confidence: 99%

High-Temperature Luminescence Quenching of Colloidal Quantum Dots

et al. 2012

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A high luminescence efficiency is an important property of colloidal quantum dots (QDs), and quantum yields higher than 90% have been reported for coreÀshell QDs. 1 High efficiencies are especially important for application of QDs as luminescent biolabels, 2 in QD lasers, 3 in spectral converters for warm white LEDs, 4,5 electroluminescent devices, 6 and solar concentrators. 7 Luminescence efficiencies are strongly temperature-dependent. 8 Extensive temperature-dependent luminescence studies for colloidal QDs have been conducted at cryogenic temperatures (0.3À300 K). 9À15 In this temperature region, interesting effects were observed, including a prolonged lifetime below 20 K related to brightÀdark state splitting, 11,16 thermally activated quenching due to surface defect states, 9,10,17 and temperature antiquenching assigned to a phase transition in the capping layer. 14,15 However, the luminescence properties of QDs above room temperature (RT) are hardly investigated, and yet, for most applications in luminescent devices, the working temperature is higher than 300 K. An interesting example is the recent application of QDs as color converters in warm-white LEDs, 18 in which QDs serve as narrow band red emitters under excitation with blue light from a (In,Ga)N LED. The narrow emission bandwidth renders QDs superior to classical phosphors based on broad band emission from luminescent ions. 19 In high-power LEDs for general lighting applications, the heat generated in the pÀn junction and phosphor converter layer leads to temperatures as high as 150À200°C in the layer applied on top of the blue diode. 20 To avoid these high temperatures, the QD phosphor layer can be placed in a more remote configuration. Still, temperatures in such a configuration are expected to be well above 50°C due to heat dissipation of the QDs themselves (excess energy from converting the blue into red light). Clearly, the quenching of QD luminescence at elevated temperatures is relevant for application of QDs in luminescent devices, and a better insight in the quenching behavior is needed.Despite its importance, research on luminescence temperature quenching above RT is very limited for QDs. It is theoretically expected for a QD to have a very high luminescence quenching temperature (T q ). Three generally accepted mechanisms for thermal quenching involve thermally activated crossover from the excited state to the ground state, multiphonon relaxation, and thermally activated photoionization. The first mechanism is generally depicted in a simple configurational coordinate diagram. 8,21 The energy difference between the minimum * Address correspondence to a.meijerink@uu.nl.Received for review July 18, 2012 and accepted September 14, 2012. Published online 10.1021/nn303217qABSTRACT Thermal quenching of quantum dot (QD) luminescence is important for application in luminescent devices. Systematic studies of the quenching behavior above 300 K are, however, lacking. Here, high-temperature (300À500 K) luminescence studies are reported for highly ef...

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“…Van Dijk and Schuurmans [163,164] developed a modified energy gap law for nonradiative decay where only a few phonons participate in the transition of the form…”

Section: Multiphonon Relaxationmentioning

confidence: 99%