Highly efficient color mixing system for the fine-tuning of white light–PLEDs using blue and red poly-chromophores

Abstract

The fine tuning of color and white light emission was achieved from the simple blending of two different types of polychromophores. The π-conjugated polymeric chromophores (blue and red) were synthesized and characterized for white light polymer emitting diode (WPLED) applications. The binary luminescent materials, Blue polymeric chromophore (BPy) and (Red polymeric chromophore (RPy), were obtained from the respective monomers via a standard Suzuki coupling reaction. The tuning of colors and white light emission were attained directly mixing of two polymeric chromophores (blue, red) in different ratio. The prepared polymer materials were confirmed using standard tehniques such as, Fourier transform infrared (FT-IR) and 13C and 1H-nuclear magnetic resonance (NMR) spectroscopy, while the gel-permeation chromatography result revealed the polymeric properties of the materials. The polymeric materials surfaces morphologies were analysed throught the FE-SEM and AFM analysis. The TGA (Thermogravymetric analysis) used to study the thermal property of the two prepared polymeric materials. The UV–visible and fluorescence spectrophotometry was applied to examine the optical features of the materials. The BPy and RPy polymers shows absorption peaks at 375 nm and 426 nm, respectively. The obatined emission peaks of BPy and RPy are at 426 nm and 603 nm, respectively. These results show that BPy and RPy belong to the blue and red emissive categories, and the white light emission was obtained with the mixing ratio of BPy(80%)-RPy(20%). The bandgap of these materials was calculated by cyclic voltammetry, and the theoretical bandgap of the materials was calculated by density functional theory analysis. Finely structured devices were fabricated, and the efficiencies of the BPy, RPy, and BPy-RPy were analyzed to assess the luminance productivity of the materials. In summary, this paper proposes a simple method to achieve white color emission by mixing polymeric chromophores at different ratios.