Exciton formation and light emission near the organic-organic interface in small-molecule based double-layer OLEDs
| Autor: | Raj René Janssen, M Marco Carvelli, HP Loebl, R Reinder Coehoorn, van A Alexander Reenen |
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| Přispěvatelé: | Molecular Materials and Nanosystems, Molecular Biosensing for Med. Diagnostics, Macromolecular and Organic Chemistry |
| Jazyk: | angličtina |
| Rok vydání: | 2012 |
| Předmět: |
010302 applied physics
Double layer (biology) Materials science business.industry Exciton 02 engineering and technology General Chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences 7. Clean energy Electronic Optical and Magnetic Materials Biomaterials Wavelength 0103 physical sciences Materials Chemistry OLED Optoelectronics Quantum efficiency Light emission Electrical and Electronic Engineering 0210 nano-technology business Layer (electronics) Diode |
| Zdroj: | Organic Electronics, 13(11), 2605-2614. Elsevier |
| ISSN: | 1566-1199 |
| Popis: | We investigate the efficiency and emission color of small-molecule based double-layer organic light-emitting diodes (OLEDs) based on 4,4′-bis[1-naphthyl (phenyl) amino]-1,1′-biphenyl (α-NPD) and aluminum (III) bis (2-methyl-8-quinolinato)4-phenylphenolato (BAlq) by studying the charge transport and photophysics near the organic–organic interface between the emitting layers. For that purpose, the light-emission profile is reconstructed from full angle, wavelength and polarization dependent electroluminescence spectra. By increasing the thickness of the BAlq layer from 100 to 300 nm, at a fixed 160 nm α-NPD layer thickness, the emission color is found to vary from deep blue to green, yellow-green, white and back to blue. We demonstrate that this is due to a gradual emission profile shift, in combination with a wavelength and layer thickness dependent light outcoupling efficiency. The emission profile shift, from an approximately 20 nm-wide zone on the α-NPD-side of the interface to a very narrow zone on the BAlq-side of the interface, gives rise to a changing balance between the contributions from BAlq excitons, α-NPD excitons and charge-transfer excitons. It also contributes to a pronounced layer thickness dependence of the external quantum efficiency. The shift of the emission profile is explained by a charge transport and recombination model. |
| Databáze: | OpenAIRE |
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