Luminescence characteristics of PPV-yttrium oxide nanocomposite layers for photonic devices

Summary form only given. The luminescence characteristics of polymer based optoelectronic devices can be modified and improved by embedding crystalline nanoparticles within the polymer matrix. There exist a few experimental indications of the influence of dielectric inclusions in conducting polymers on photoelectric properties without revealing a clear physical picture. We provide herein a detailed analysis of this problem for the particular system of Y/sub 2/O/sub 3/ inclusions in a PPV matrix. Contrary to semiconductor quantum dots, dielectric nanocrystals with large band gap play the role of antidots -potential bumps for carriers. Experiment reveals the following modification of PPV luminescence spectrum caused by dielectric inclusions: the luminescence maximum shifts to a shorter wavelength of approximately 460 nm; the maximum becomes wider; the new spectrum no longer contains distinct vibronic structure; the luminescence kinetics is non-exponential but contains a noticeable component with /spl tau/ = 0.4 ns typical for pure PPV. Electroluminescence spectra are also shown for pure PPV and PPV/Y/sub 2/O/sub 3/ nanocomposites at the same injected current density. In addition to the spectral and time-resolved features described above in the context of photoluminescence, the composite structures demonstrate a considerable increase in the luminescence intensity for a given injected current density. The nonuniform current density in the composites creates regions of high local electric fields with intense light emission. The results obtained demonstrate that dielectric nanocrystals can essentially modify luminescent properties of conducting polymers, offering one avenue to improved efficiency and spectral tailoring for applications in light-emitting devices.