Polymer white light emitting diodes applications of benzotriazole and fluorene derivatives

Koçak, Güler
In this thesis, white polymer light emitting diodes (WPLEDs) were constructed using benzotriazole and fluorene containing conjugated polymers. For this purpose, three different blue and four different orange emitting conjugated polymers with different end cappers were used. The method that was used throughout the thesis included mixing of two polymers (blue and orange emitting) having different weight ratios in a common solvent. These solutions were coated on ITO-glass substrates by spin-coating technique which is the most common method for polymer coating. The different ratios of the two polymers were optimized according to the luminance efficiency of OLED devices. Moreover, an optimization study was conducted for different solvents such as toluene and chloroform. The polymers that were synthesized throughout the thesis were characterized by means of NMR, GPC, TGA and DSC. Polymers were also characterized for determining their fluorescence quantum yield prior to the device fabrication. In addition, all polymers and polymer blends were spin coated onto silicon wafers in order to examine the active layer thickness via Atomic Force Microscopy (AFM). After determination of the optimum film thickness, WPLED devices were constructed. The flexible WPLED device experiments were also conducted, and all constructed devices were characterized by means of their luminance, color coordinates and luminance efficiency. As a result, WPLEDs from fluorescent polymer blends showed effective CIE color coordinates of x=0.31, y=0.33 which are very close to the pure white color (x=0.33, y=0.33), and all devices showed high stability and have voltage invariant electroluminescence spectra.