Electroluminescence measurement

Fig. 16 Parameters for defining the charge-transfer state energy cx in organic solar cells. Charge-transfer state energy for MDMO-PPV PCBM blend device determined by Fourier transform photocurrent spectroscopy and electroluminescence measurements. Reprinted figure with permission from [188]. Copyright 2010 by the American Physical Society...

Luminescence Spectra from n-TiCh and n-SrTiCh Semiconductor Electrodes and Those Doped with Transition-Metal Oxides As Related with Intermediates of the Photooxidation Reaction of Water. Mechanistic aspects clarified using photo-and electroluminescence measurements. 407... 

The above technique requires organic layers that are of the order of a few microns thick, considerably thicker than those used in OFEDs. A way to measure charge carrier mobilities directly on an OFED geometry is by time-resolved electroluminescence measurements. The technique is based on the fact that for recombination to take place, the most mobile of the two carriers needs to transverse the sample and meet with the less mobile one [120, 121]. Therefore, the time onset for emission corresponds to the transit time of the most mobile carrier. Blom et al. [122] have described a high sensitivity variation of this technique where the time integrated light output is measured as a fimction of the duration of a voltage pulse and the transit time is extracted by extrapolation to... 

This means that in these blends the spectral shape of the electroluminescence would be independent of whether process (a) or (b) in Fig. 2.1 occurs because ex-citons could quickly transfer towards a nearby interface site. In well-mixed blends it is therefore impossible to show that the exciplex is the primary product of charge capture and hence to prove that barrier-free capture occurs. We address these concerns here by presenting electroluminescence measurements from bilayer light-emitting diodes, where leakage currents are prevented, while a low density of interface sites (in fact the lowest possible) is maintained. 

The field effect mobility may also be decreased by interface states. This is supported by the increase of the field effect mobility by using different insulators [250, 350]. Also drift mobilities extracted from electroluminescence measurements show a thickness dependence pointing to an influence of the interface [351],... 

Fig. 9.7 Electroluminescence measurements on a plasmon-enhanced DUV-LED. (a) Top-emission EL spectra from the LED sample without A1 nanoparticles and with A1 nanoparticles deposited on the top surface, as well as the enhancement ratio between them, (b) Bottom-emission EL spectra of the LED samples without A1 nanopaiticles and with A1 nanoparticles deposited on the top surface, as weU as the enhancement ratio between them (Huang et al. Scientific Reports 4, 4380, doi 10.1038/srep04380)...

Fig. 4 Temperature and electric field dependence of charge carrier mobility obtained firom transient electroluminescence measurements. Theoretical fits ate shown in solid lines. From [24]...

The setup for transient electroluminescence measurements is shown schematically in Figure 24. 

Ordered dialkoxy PPV derivative has been prepared by Yoshino et al. [491. oly(2 -nonoyloxy-1,4-phenylene vinylene) 27a forms a nematic liquid-crystalline phase upon melting. The material retains its order upon cooling to room temperature, and its band gap (2.08 eV) is measurably smaller than in an unoricnted sample. Oriented electroluminescence may be achieved by rubbing a thin fdin of the material to induce molecular orientation [50],... 

Figure 6-23. Sketch of the experimental arrangement tor measuring the angular dependence or lluores-ccncc and electroluminescence. The viewing angle 0 is varied between -90 " and +90 .

Two main methods have been used to measure the charge carrier mobility in electroluminescent polymers time of flight (TOF) carrier transit time measurements and analysis of the current-voltage (1-V) characteristics of single carrier devices in the space charge-limited current (SCLC) regime. A summary of the results for the hole mobility of PPV and PPV-related polymers is given in Table 11-1 [24, 27-32]. For... 

Figure 5-24. u) Polar represenlalion (Irom —90 io +90 ) lor lire angular dependence ol lliioreseenee anisotropy (ll-V) in Th films willi grain sizes of 1500 mil (open squares). 000 nm (filled circles), and 200 nm (open circles), b) The angular dependence of electroluminescence anisotropy (H-V) measured from the LED contacted pari of the same samples. 

A.J. Campbell, D.D.C. Bradley, and H. Antoniadis, Dispersive electron transport in an electroluminescent polyfluorene copolymer measured by the current integration time-of-flight method, Appl. Phys. Lett., 79 2133-2135, 2001. 

Spiro-FPAl/TPBI/Bphen Cs/Al. A very low operating voltage of 3.4 V at luminance of 1000 cd/m2 was obtained, which is the lowest value reported for either small-molecule or polymer blue electroluminescent devices. Pure blue color with CIE coordinates (0.14, 0.14) have been measured with very high current (4.5 cd/A) and quantum efficiencies (3.0% at 100 cd/m2 at 3.15 V) [245]. In another paper, Spiro-FPA2 (126) was used as a host material with an OLED device structure of ITO/CuPc/NPD/spiro-FPA2 l%TBP/Alq3/LiF that produces a high luminescent efficiency of 4.9 cd/A [246]. 

FIGURE 9.13 Optoelectronic characteristics of AM-PLED, (a) Calculated display luminance and estimated display luminance versus /data characteristics, (b) measured Paata evolution with the /data, and (c) PLED and AM-PLED electroluminescent (EL) spectra are shown. The CIE color coordinates of the PLED and AM-PLED are also shown in the inset of this figure. (From Hong, Y., Nahm, J.-Y., and Kanicki, J., IEEE J. Selected Top. Quantum Electron. Org. Light-Emitting Diodes, 10, 1, 2004 With permission.)... 

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