Fabric, electron emission spectra

For the samples comprising of PAA coated with Eu-doped xerogel typical PL spectrum measured at the excitation wavelength of 368 nm is presented in Fig. 2. It reveals the presence of clearly pronounced PL band at 475 nm visible to the naked eye which corresponds to inherent blue photoluminescence of PAA. Well-resolved optical band at 613 nm corresponding to Do-> F2 electron transition of Eu ions in the fabricated structure is also observed from the spectrum but red emission can not be seen with the naked eye. 

LEDs were fabricated with TA-PPP as the emissive layer. Single-layer devices of ITO/PEDOT/TA-PPP/Ca/Al were fabricated. PEDOT, poly(3,4-ethylenedioxythiophene), was used to enhance hole injection from the anode. Charge injections of the single layer LEDs were clearly hole dominant The barrier for electron injection, around 1.0 eV, is too high. Electron dominant materials such as DO-PF and 2-(4-t-butylphenyl)-5-biphenyloxadiazole (t-PBD) were used to enhance electron injection. The thin film of a TA-PPP and PF blend (95 5 weight ratio) was phase separated. Atomic force microscopy (AFM) showed PF spheres, close to 1 pm in diameter, dispersed in the TA-PPP matrix (Figure 6). This type of phase separation is common in blends of stiff and soft polymers. The PL emission of die blend film was characteristic of TA-PPP. However, once thermally treated, the spectrum shifted bathochromically much like PF. The EL spectrum from LEDs based on the blend thin film contained much emission from PF in the 500-700 nm regime. The device efficiency was about 0.43 cd/A. TA-PPP/PF double layer LEDs were also fobricated. But the efficiency was not improved because when PF was spin coated onto TA-PPP, the PF solution washed out most of the TA-PPP layer. 

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