Devices photoluminescence spectra

The zone of recombination can be very small as was shown by Aminaka et al. [225] by doping only a thin layer (5 nm) in the device by a red emission material. By observing the ratio of host and dopant emission, the authors were able to show that the recombination zone of the device was as thin as 10 nm. The emitted light is usually coupled out at the substrate side through the transparent anode. As a rule, the electroluminescence spectrum does not differ much from the photoluminescence spectrum. 

It is well known that solid-state LECs exhibit a significant response time since electroluminescence can only occur after the ionic double-layers have been built up at the electrode interfaces [79,82]. Since in this case only the PFg anion is mobile, the double-layers are formed by accumulation and depletion of PFg at the anode and cathode, respectively. The LEC device with 45 started to emit blue-green light at a bias of 5 V after several minutes. The electroluminescence spectrum, as shown in Fig. 36 (trace a), is very similar to the photoluminescence spectrum recorded for a spin-coated film on glass and of a solution of the complex. For comparison, the electroluminescence... 

Figure 10-14. Inset Photoluminescence spectrum for low excitation pulse energy Ep Main part (a) displays the spectrum for pump pulse energies well below the lasing threshold while (b) shows the spectrum obtained for excitation with a pump energy close to the lasing threshold (c) presents the single mode-lasing spectrum emitted when the device is pumped well above threshold. The dashed lines indicate the zero line which is arbitrarily shifted in case of (b) and (c).

Fig. 2 PSi microcavity-based detection of bacteriophage lambda (adapted from [9]). The solid line represents the photoluminescence spectrum of the DNA-derivatized device, while the dotted line shows the photoluminescence spectrum of the sensor following exposure to the bacteriophage virus...

In organic LEDs, the electroluminescence spectrum is quite similar to the photoluminescence spectrum of the polymer used in the device (Fig. 12), so that the light emission is attributed to the singlet exciton decay. The excitons are formed by electrons and holes injected into the polymer by the cathode and anode, respectively. The injection current density depends on several parameters such as the potential barriers for charge injection at the polymer-electrode interfaces, the mobility of the charge carriers in the polymer layer, the polymer layer thickness, and the applied voltage. The efficiency of these devices is intrinsically limited by the balance between injected electrons and holes and by the fraction of excitons that decay radiatively. Further efficiency limits are imposed by reflections that occur in the interfaces between the materials that compose the device, including the interface formed... 

Poly(p-phenylenevinylene) derivatives are promising candidates for the active layer of polymer light-emitting diodes. Thus, various types of substituted poly(p-phenylenevinylene)s have been synthesized. Whereas these derivatives are soluble in organic solvents, a high-quality thin film of these polymers can be formed. Die optical properties of these polymers have been reviewed previously [8, 169]. The electroluminescence spectrum of the device fabricated with a conjugated pofymer is almost the same as that of the photoluminescence spectrum of the thin film of the polymer. The peaks in photoluminescence spectra are compiled in Table XVII [170, 171]. 

Recently, photoluminescence properties of boron carbide nanowires were being studied and reported. Photoluminescence spectrum of a thin film made out of B4C nanowires exhibited a broad band at 638 nm, which strongly suggests the potential application of boron nanowires in visible optical devices. Nonetheless, nanowire and nanorod structures based on boron carbide find their application in different areas, including field emission devices and thermoelectric energy converters, neutron adsorbent in nuclear industries, and especially in composite materials as reinforcing agents. ... 

The electroluminescence spectra of the single-layer devices are depicted in Figure 16-40. For all these OPV5s, EL spectra coincided with the solid-state photoluminescence spectra, indicating that the same excited states are involved in both PL and EL. The broad luminescence spectrum for Ooct-OPV5-CN" is attributed to excimer emission (Section 16.3.1.4). 

Fig. 1. Absorption and photoluminescence dashed line) spectra of a thin film of LPPP 26 and electroluminescence solid line) spectrum of an ITO / LPPP 26 (60 nm) / A1 device (from [50])...

The narrow photoluminescence (PL) spectrum of these NCs are widely tunable across the visible spectrum to adjust white light parameters, whereas the conventional yellow phosphorus has a fixed PL spectrum. By using the size effect, these NCs can fully cover the visible spectrum from blue to red as shown in Fig. la-d. Additionally, the small overlap of the NC emission and absorption spectra provides the ability to tune the white light spectrum conveniently. We carefully design and implement hybrid device parameters such as the order and thickness of the NC films and type and density of NCs as necessary to generate white light with the desired characteristics. 

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