PL lifetimes

The exponent f describing the distributions of PL decay rates is found to be in the range 0.4—0.5 for most temperatures and PL energies investigated. In contrast, the PL lifetime r decreases with increasing PL energy. 

The PL lifetime values r obtained by fitting a stretched exponential function decrease with increasing PL peak energy PPL. For micro PS dried in a vacuum, for which the PL energies range from 1.5 to 3.5 eV, this dependence can roughly be fitted to the empirical relation ... 

Mason et al supported the two step process based on the decrease in relative intensity with below bandgap excitation [19]. Partially based cm their PL lifetime studies, Hofmann and co-workers have argued that the spin-dependent process is a radiative transition from a shallow donor to a much deeper single donor [20,21], The basic argument that there is a level in the lower half of the bandgap with a broad line having a g value a little less than two has been supported by Reinacher et al based cm their LESR results [13],... 

Relaxation processes in the triplet state T of Ir(acac)(btp)2 doped in pc and cbp fluorescent materials have been investigated by Tsuboi and Aljaroudi . They found good agreement between the calculated and observed temperature dependence of the PL lifetime and intensity for these doped materials. 

In this paper, we present some of our results on Si nanowires and quantum dots. The PL lifetime is calculated as a function of the crystallographic direction and the size of the wires and the dots. We have considered sizes in the range of 1-4 nm and crystallographic directions varying in (100) plane from [100] to [110] direction. Here, we discuss representative results on wires and dots of size 2 nm. 

Figure 2. The calculated PL lifetime as a function of the wire orientation, at room temperature, for the I subband (dots) and for the D subband (squares). The dashed line is for the direct transitions of the I-subband and the dotted line is for the phonon-assisted transitions of t he I -subband. T he s olid 1 ine i s for the total PL lifetime of the quantum wire.

The above distinct features of the PL lifetimes when electrons occupy the I subband or the D subband show that the lifetime strongly depends on the electronic structure of the quantum wire. Thermal activation from one subband to the other is also important as it is shown in the following analysis. At low temperatures, only the ground subband is occupied and the dependence of the lifetime on the wire direction is shown in Fig. 1 by a solid line. At room temperature, occupation of the first excited subband may be activated and the resulting lifetime is then given by the following expression ... 

The calculated PL lifetimes for the two levels as a function of the dot orientation at room temperature are presented in Fig. 4. The lifetime for the [001] valley level does not depend on the dot orientation. First order and second order transitions dominate depending on the dot orientation. The magnitude of the lifetime depends on the confinement dimensions and phase of the wavefunction that for the dots as for the wires is given analytically within EMA [32]. The electron that... 

Fig. 3.10. PL lifetime of DPVBi/Ru(dpp) sensors with different sensing elements, (open circle) spin-coated sol-gel prepared from a sol containing 2.5mg mL GOx, (open triangle) spin-coated sol-gel prepared from a sol containing 7.5 mg mL GOx, open square) solution-based sensing element, and open diamond) drop cast film prepared from 30 xl containing 7.5 mg mL Ru(dpp) and 7.5 mg mL GOx. Excitation was obtained using a blue DPVBi OLED...

It should be noticed that the size dependences of to and p are sensitive to temperature. Indeed, the Er3+ PL lifetime is longer and its size dependence is weaker at low... 

PL lifetimes were also examined at product concentrations and are shown in Figure 10. In pure buffer, the lifetime was measured to be 10 psec and, in the presence of j-nitro-phenol, the lifetime was measured to be 6 psec. This decrease indicates the presence of p-nitro-phenol partially quenching the fluorescence. Combining this observation with the PL reduction correlated with p-nitro-phenol build-up, as shown in Figures 9 and 10, indicates the PL is partially quenched by a reversible mechanism, most likely charge transfer between the p-nitro-phenol and the PSi surface. 

Host lattice Reference Structure ZPL emission EX (nm) EM (nm) External QY (%) PL lifetime (ms)... 

The F-band, with emission peaks around 415 70 nm, FWHM of 0.38-0.5 eV, and quantum efficiencies of 0.1 % at best, has been reported in various thermally or chemically oxidized PSi samples (Koyama and Koshida 1997 Qin et al. 1997 Cullis et al. 1997 Bisi et al. 2000 Canham 1997). The PL lifetime is in the nanosecond range. Many reports have attributed this band to oxide-related defects or contamination (occurring upon storage and prolonged exposure to air) by organic chromophores (e.g., carbonyl groups) (Loni et al. 1995). Recently, another origin has been... 

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