| Abstract [eng] |
In theory, phosphorescent organic light emitting diodes could reach internal quantum efficiencies of up to 100%. Despite that, technology used today lagging far behind theoretical maximum. To further develop this type of light generating appliances it is essential to design and synthesize new materials with better properties and to apply them in new structure efficient devices. In this work, new polyethers containing pyridinyl-substituted carbazole rings were synthesized and characterised. Best device showed 11.7 cd/A current efficiency and 5.4 lm/W power efficiency at 1000 cd/m2 luminance, which is used for illumination purposes. During this project another electron donor was used. Phenoxazine-based derivatives were synthesized and characterized. Thermal and optoelectrical properties of objective materials were investigated and suitable materials were used as hosts in green organic light emitting devices. Peak performance was demonstrated by a device using 3-[bis(9-ethylcarbazol-3-yl)methyl]-10-hexilphenoxazine host. Diode exhibited maximum luminance of over 5360 cd/m2, external quantum efficiency and current efficiency was 5.9% and 18.3 cd/A, respectively. Third generation organic light emitting diodes could reach internal quantum efficiency of 100% using thermally activated delayed fluorescence deploying fully organic materials instead of heavy metal complexes, which were used in second generation (phosphorescent) devices. By using this mechanism of photon generation lifetime of triplet exited states typically is shorter and undesirable process of triplet-triplet annihilation could be avoided. During this project, new structure TADF materials using benzophenone base and alkyl-substituted bicarbazole were synthesized and characterized. After assessing thermal and morphological properties of new derivatives it was discovered that all objective materials were fully amorphous with high glass transition temperatures. All compounds were tested as emitters in organic light emitting devices. Best overall performance was demonstrated by device using 15 % of 4,4’-bis(9’-octyl-[3,3’]-bicarbazol-9-yl)benzophenone emitter doped in a host. External quantum, current and power efficiency peaked at 4,0%, 9,1 cd/A and 7,9 lm/W, respectively. During the master’s final degree project technological scheme for the production of benzophenones with alkyl-substituted bicarbazole fragments was developed. Based on health risk factors of materials needed in the synthesis occupational safety recommendations were described. |
