Temperature dependent photoluminescence

M. Ariu, D.G. Lidzey, M. Sims, A.J. Cadby, P.A. Lane, and D.D.C. Bradley, The effect of morphology on the temperature-dependent photoluminescence quantum efficiency of the conjugated polymer poly(9,9-dioctylfluorene), J. Phys. Condens. Matter, 14 9975-9986, 2002. 

FIGURE 3 Temperature dependent photoluminescence of a homoepitaxial GaN layer (0.4 p.m) grown by RMBE. At 4 K photoluminescence linewidths of the bound excitons are as narrow as 0.5 meV (after [31]). 

Xia Z, Li G, Chen D, Xiao H (2009) Synthesis and calcination temperature dependent photoluminescence properties of novel bromosilicate phosphors. Mater Lett 63 2600... 

These results indicated that the major diffusion mechanism of Pt in GaN was possibly an interstitial diffusion. In addition, it was also observed that the Pt atom may be a donor because the carrier concentration in Pt-diffused GaN was higher than that in un-diffused GaN. The optical property was studied by temperature-dependent photoluminescence measurement. The thermal quenching of the photoluminescence spectra for Pt-diffused GaN samples was also examined. 

There is also another pathway to arrive at the state that goes via the excited state of Er, generated through relaxation from the j j 2 state, through a non-resonant non-radialive energy transfer step by interaction with a nearby excited Yb ion. Which process is dominant is often a subtle result of several effects, such as crystal field splitting, and so on, and would require detailed (time-resolved and temperature-dependent) photoluminescence studies to unravel. Further discussion is beyond the scope of this review. 

The best fit is obtained with B = 100 K and A = 2.4 X I0-4 eV K l. These values are closed to those obtained from the bulk phase (B = 180 K and A = 4 x I0-4 eV K l, respectively) (76). On decreasing temperature, the PL intensity increases and its maximum is shifted to higher energy. To determine the peak intensities and positions, the PL spectrum is simulated as before by assuming two Gaus-sians. The temperature dependence of the photoluminescence due to direct transition obeys an Arrhenius law given by (34) ... 

Currently silicon is still one of the most important semiconductors as it is the basis of any computer chip. It exhibits an indirect band gap of 1.1 eV at room temperature in the microcrystalline phase. Similar to Ge, silicon nanoparticles show a size-dependent photoluminescence. It was reported by Katayama el al. that a thin Si layer can be electrodeposited in l-ethyl-3-methylimidazolium hexafluorosilicate at 90 °C [44], However, upon exposure to air the deposit reacted completely to SiC>2, which makes it difficult to decide whether the deposit was semiconducting or not. Recently, we showed for the first time that silicon can be well electrodeposited from SiCU in the air and water stable ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([BMPJTfiN) [45, 46]. This ionic liquid can be... 

Numerous articles have appeared on poly(arylene vinylene) systems, acetylenes and related polymers. The temperature dependence of the photoluminescence from poly(p-phenylene vinylene) (PPPV) has been examined in terms of its influence on diffusion rates while a magnetic field has been found to enhance luminescence intensity. A series of poly(alkoxyphenylenes) have been synthesised with high luminescence quantum yields whereas vapour deposited poly(p-phenylene vinylene) has been found to have an unidentifiable defect structure when annealed at high temperatures. ... 

Fig. 16 Temperature dependent emission intensity from TPP dopants in a PF2/6 host. The host is optically excited and the TPP guest is populated by a combination of Forster transfer and exciton migration. Data is corrected for the temperature dependencies of the host and guest photoluminescence quantum yields...

The photophysics of jt-conjugated polymers are reviewed in detail in other chapters of this book. (See, for example, Chapter 3.) Here, we focus on the electronic and photophysical phenomena that occur at the heterojunction between two different semiconductor polymers. The heteroj unctions are formed by combining four different polyfluorene copolymers in blend or bilayer thin films and are investigated using time-resolved and steady-state, temperature- and elec-tric-field-dependent photoluminescence measurements as well as electroluminescence and time-resolved spectroscopy. We review a body of work carried out in our laboratories over the last few years, and published in numerous journal articles (see refs. [13-17]). 

We report on the efficient photoluminescence up-conversion in colloidally synthesized CdTe nanocrystals. We demonstrate that the efficiency of photon energy up-conversion and the magnitude of the spectral shift can be controlled by (i) the size of the nanocrystals (ii) the temperature dependence of the excited state absorption coefficient (iii) the excitation intensity. We suggest that intrinsic gap states are involved as intermediate states in the up-conversion rather than nonlinear two-photon absorption or Auger processes,... 

One comment on the temperature dependences of the exciton line widths in CuBr and Agl based ternary conpound is that it is quadratic in the former and linear in the latter case. A good spectral resolution is necessary to detect the small confinement contribution at low temperatures. Measmements with smaller dots would reveal sizeable confinement effects and photoluminescence measurements... 

The electrical characterization was performed by means of DC measurements. The optical characterization included temperature-dependent (10-100 K) photoluminescence (PL) spectroscopy at low excitation (325 nm, 2 W/cm2), and low-temperature (10 K) reflection spectroscopy. Photoreflectance (PR) spectra were measured using the same HeCd laser beam with a power density of 0.1 mW/cm2 for modulation of internal electric fields. 

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