No abstract

A new series of blue light-emitting 2,4-diphenylquinoline (DPQ) substituted blue light-emitting organic phosphors namely, 2-(4-methoxy-phenyl)-4-phenyl-quinoline (OMe-DPQ), 2-(4-methyl-phenyl)-4-phenylquinoline (M-DPQ), and 2-(4-bromo-phenyl)-4-phenylquinoline (Br-DPQ) were synthesized by substituting methoxy, methyl and bromine at the 2-para position of DPQ, respectively by Friedländer condensation of 2-aminobenzophenone and corresponding acetophenone. The synthesized phosphors were characterized by different techniques, e.g., Fourier transform infra-red (FTIR), differential scanning calorimeter (DSC), UV-visible absorption and photoluminescence spectra. FTIR spectra confirms the presence of chemical groups such as C=O, NH, or OH in all the three synthesized chromophores. DSC studies show that these complexes have good thermal stability. Although they are low-molecular-weight organic compounds, they have the potential to improve the stability and operating lifetime of a device made out of these complexes. The synthesized polymeric compounds demonstrate a bright emission in the blue region in the wavelength range of 405-450 nm in solid state. Thus the attachment of methyl, methoxy and bromine substituents to the diphenyl quinoline ring in these phosphors results in colour tuning of the phosphorescence. An electroluminescence (EL) cell of Br-DPQ phosphor was made and its EL behaviour was studied. A brightness-voltage characteristics curve of Br-DPQ cell revealed that EL begins at 400 V and then the brightness increases exponentially with applied AC voltage, while current-voltage (I-V) characteristics revealed that the turn on voltage of the fabricated EL cell was 11 V. Hence this phosphor can be used as a promising blue light material for electroluminescent devices.

The importance of artificial light has long been recognized as it extends the day. Copious corporations and academic institutions are investing cosmic treasures in tracking down the advanced artificial lighting applications with a vision towards energy efficient and eco-friendly solid state lighting. In this regard, organic light-emitting diodes (OLEDs) are going to change the human lifestyle, by offering a promising avenue to develop future energy saving solid-state lighting sources because of their intrinsic characteristics such as low driving voltage, high resolution, high brightness, large viewing angle, large color gamut, high contrast, less weight and size, efficiency etc., there by dictating their ability to reach the pinnacle in the field of flat panel displays and solid state lighting sources. With the goal towards future application, many design strategies like synthesis of novel materials, well judged anatomy of device configuration, development of refined and low cost fabrication techniques have been put forward to achieve high efficiency, good color stability and quality lighting. Practical applications, which enrich the ideas of the specialists in this field to develop new routes for future research development of OLEDs are enumerated and illustrated by specific examples. This chapter also integrates the novel approaches for energy efficient and eco-friendly solid state lighting as well as the limitations and global haphazards of currently used lighting systems. The current state of the art, ongoing challenges and future perspectives of this research frontier to reduce the driving voltage, minimization of degradation issues, enhance their life time are illustrated. Review on the status and future outlook of these OLEDs strongly reveals their emergence in the next few years.

No abstract

No abstract