4‐(dicyanomethylene)‐2‐methyl‐6‐(p‐dimethylaminostyryl)‐4H‐pyran (DCM)‐doping density dependence of luminescence spectra and white emission in polymer light‐emitting diodes

Abstract

We fabricated white polymer light‐emitting diodes (PLEDs), in which the active region is doped with a low‐weight molecule. The host polymer material is Poly(9,9‐didodecyl‐fluorenyl‐2,7‐yleneethylnylene) (PFO), while the guest luminescent low‐weight‐molecule is 4‐(Dicyanomethylene)‐2‐methyl‐6‐(p‐dimethylaminostyryl)‐4H‐pyran (DCM). The photoluminescence (PL) and electroluminescence (EL) spectra strongly depend on DCM‐doping‐density. However, the most suitable DCM‐doping‐densities for white emissions in PL and EL are slightly different. This discrepancy is caused by the difference in excitation efficiencies. The photo‐excitation system for PL measurement is better than the current injection for generating carriers efficiently. Thus, the realization of the white EL signal requires the larger DCM‐doping‐density than that of the white PL signal. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Ternary complex [Sm(acac)3(5-Br-2,2′-bpy)] for the solution-processed white polymer light-emitting diode (WPLED)

“…With regard to the singlet ( 1 ππ*) energy level (27855 cm 1 ) estimated from the lower wavelength (359 nm) of its UV-visible absorbance edge, the energy gap ΔE 1 ( 1 π-π* -3 π-π*, 4760 cm 1 ; Fig. 1S) near to the desirable 5000 cm 1 , endows a relatively effective ISC process according to the Reinhoudt's empirical rule [18]. Meanwhile, ruled by the Latva's empirical rule [19], the second energy gap ΔE 2 (5171 cm 1 ; 3 π-π*-4 G5/2) between the ligands-based 3 π-π* energy and the first excited state 4 G5/2 (17924 cm 1 ) of Sm 3þ ion is large enough to sensitize the Sm 3þ -centered orangelight.…”

Self-Organized One-DimensionalTiO2Nanotube/Nanowire Array Films for Use in Excitonic Solar Cells: A Review

“…Further, the pore size dimensions should be small enough so that the nonradiative energy transfer events happen in close proximity. In the present work, the empty space (i.e., pores) of Red/Near IR absorbing SQ-1 organic dye [7,71] coated transparent TiO 2 nanotube array films [35,38,72,73], 500 to 600 nm in length with 20-28 nm pores on fluorine-doped tin oxide-coated glass, were filled with Spiro-OMeTAD [74] blended with a visible light absorbing 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran, DCM-pyran [75], donor molecules. The calculated Förster radius is 6.1 nm.…”

“…The nanometer-scale nanotube pores, intercalated with the hole transporting materials, provide a facile path for hole transport. The energy level positions of the selected donor, DCM-pyran [75], and acceptor, SQ-1 dye [7], with respect to Spiro-OMeTAD [15,90,91] (Typical physical data of Spiro-OMeTAD, provided by EMD Chemicals (Merck KGaA, Darmstadt, Germany): HOMO energy ∼ −4.9 eV, LUMO energy ∼ −1.9 eV, Band gap ∼3.0 eV, Glass transition temperature T g ∼120 • C, Melting point T m ∼246 • C, Purity >99.9% (Test procedure-HPLC). Note: the energy levels are determined using cyclic voltammetry and UV-VIS; these values are usually 0.2-0.3 eV less deep than with other optical methods (e.g., UPS).)…”

Efficient, stable and high color rendering index white polymer light-emitting diodes by restraining the electron trapping

“…It's generally considered that the larger the overlap, the stronger the energy transfer. The content of guest materials' weights usually below 1% for the polymer blend system with stronger energy transfer, which make the EL spectra pretty sensitive to its concentration so that it is quite difficult to optimize for obtaining white emission with high CRI (>90) [18][19][20]. Unlike the energy transfer, the latter scenario requires the highest occupied molecular orbital (HOMO) or the lowest unoccupied molecular orbital (LUMO) levels of guest materials (green and red) lying in the band gap of host material (blue).…”