In this study, novel copolymers consisting of blue and red chromophores are presented to induce emission tuning, enabling the definition of white light emission in a single polymeric layer. These aromatic polyether sulfones exhibit high molecular weights, excellent solubility and processability via solution deposition techniques. In addition, by carefully controlling the molar ratios of chromophores composition, the energy transfer mechanism, from blue to red chromophores, takes place enabling us to define properly the emission covering the entire range of the visible spectrum. The optical and photophysical properties of the monomers and copolymers were thoroughly investigated via NIR-Vis-far UV Spectroscopic Ellipsometry (SE), Absorbance and Photoluminescence (PL). These copolymers are used as an emissive layer and applied in solution-processed WOLED devices. The fabricated WOLED devices have been subsequently studied and characterized in terms of their electroluminescence properties. Finally, the WOLED devices possess high color stability and demonstrate CIE Coordinates (0.33, 0.38), which approach closely the pure white light CIE coordinates.

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Obtaining white light from organic LEDs is a considerable challenge and, to realize white light emission, many studies have been conducted, primarily addressing two- or three-color blend systems as a promising strategy. In this work, pristine films, grown by spin coating, consisting of commercial blue Poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO), green Poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT), and red spiro-copolymer (SPR) light-emitting materials, were studied as reference materials. Afterward, binary (SPR doped in host PFO) and ternary (SPR and F8BT doped in host PFO) thin films were successfully prepared with various ratios. The characterization of the as-grown and thermally-treated blend films was focused on their optical and photophysical properties. After, the fabrication of OLED devices on glass substrates was carried out for the evaluation of a blend’s composition and annealing in terms of the devices’ electrical characteristics and electro-emission properties in order to achieve white light emission. Their analysis provided insights into the energy transfer mechanisms between the constituent materials, which were correlated to host–guest interactions as well as to the structural changes originated by thermal treatment, leading to the crystallization of PFO. Finally, the OLEDs based on ternary blends approach the white light emission with (x, y) of (0.272, 0.346). These fabricated devices also exhibit turn-on voltages as low as 3 V, accompanied by remarkable luminance values above 3000 cd/m2.

In this work, we present the fabrication and characterization of solution-processable red Phosphorescent Organic Light-Emitting Diodes (PhOLEDs). The proposed approach is based on Ir(III) complex, namely Bis(2-(3,5-dimethylphenyl)quinoline-C,N)(acetylacetonato)Iridium(III), also known as Ir(dmpq)2(acac), which was doped in four different host materials: (a) 4,4′-Bis(N-carbazolyl)-1,1′-biphenyl (CBP), (b) 1,3-Bis(N-carbazolyl)benzene (mCP), (c) 1,1-Bis[(di-4-tolylamino) phenyl]cyclohexane (TAPC), and (d) tris(4-carbazoyl-9-ylphenyl)amine (TCTA). The metal–organic complex offers unique optical and electronic properties arising from the interplay between the inorganic metal and the organic material. The optical and photophysical properties of the produced thin films are investigated in detail using spectroscopic ellipsometry and photoluminescence, whereas the structural characteristics are examined by atomic force microscopy. This comparative study of the four different Host:Ir-complex systems provides valuable information to evaluate the emission characteristics in order to achieve pure red light. Finally, these materials were applied as a single-emissive layer in PhOLED devices, and the electroluminescence characteristics were studied.