Amplified spontaneous emission ͑ASE͒ in optically pumped polymeric films containing the luminescent and hole-transporting organic molecule N,NЈ-Bis͑3-methylphenyl͒-N,NЈdiphenylbenzidine ͑TPD͒ is demonstrated. ASE is observed in polymer films of polystyrene and poly͑N-vinylcarbazole͒ doped up to 20% with TPD. From these results, we conclude that TPD-based films are candidates for blue-emitting organic diode lasers.

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Immiscibility between dimethyl sulfoxide (DMSO) and polar solvents used for poly(N-vinylcarbazole) (PVK) solutions, leads to failed light-emitting diodes when colloidal cadmium sulfide (CdS) nanoparticles capped with thiophenol are incorporated to their active layer. To prevent this, a heat treatment is applied to the CdS nanoparticles in order to evaporate DMSO solvent. After evaporation most of the nanoparticles increased their size, and some of them show hexagonal crystalline structure instead of the original cubic zinc-blende observed in colloidal pre-treated nanoparticles. Nevertheless, enhanced electronic properties are measured in light-emitting devices when DMSO-free nanoparticles are embedded in the poly(N-vinylcarbazole) active layer. Light emission from these hybrid devices comprises the whole visible range of wavelengths as searched for white LEDs. Moreover, electroluminescence from both types of CdS nanoparticles (smaller cubic and bigger hexagonal) has been discriminated and interpreted through Gaussian deconvolution.

Energy transfer from several semiconducting organic molecules and polymers to rareearth complexes in the form of spin-cast films is reported. Energy transfer is observed in poly(N-vinylcarbazole) (PVK) films doped with various europium and samarium complexes. Polystyrene films containing the hole-transporting organic molecule 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD) and the electron-transporting molecule N,N′-bis(3-methylphenyl)-N,N-diphenylbenzidine also show energy transfer to the europium complexes, but not to the samarium ones. We show that energy transfer from PBD to the europium complexes is more efficient than from PVK. These films are semiconducting and easy to process, so they are candidates for monochromatic light-emitting diodes.

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