The as-synthesized threads were washed by immersion in tetrahydrofuran for 1 day. The final inorganic fibers were then analyzed. TEM experiments were performed with a JEOL 2000-FX microscope (accelerating voltage of 200 kV). Scanning electron microscopy (SEM) observations were performed with a JEOL JSM-840A SEM operating at 10 kV. The specimens were carbon-coated prior to examination. XRD experiments were carried out on an X'pert MPD Philips instrument using Cu Ka radiation with an average current of 50 mA. The X-ray scattering measurements were performed with a NanoSTAR apparatus (Bruker). The X-ray source was a sealed-tube X-ray generator. The Cu Ka radiation was selected with two Göbbel mirrors and collimated with three pinholes. The scattered radiation was collected on a two-dimensional detector (HI-STAR). The diffuse scattering intensity I is plotted versus the scattering vector q = (4p/k)sinh (2) where 2h is the scattering angle and k is the incident wavelength. The sample-to-detector distance was 106 cm for the SAXS experiments. To detect reflections in the wide-angle region this distance was reduced to 7 cm. The solid-state 51 V MAS NMR spectrum of vanadium oxide fibers was obtained at 105.2 MHz on a Bruker Avance 400 spectrometer using a MAS 4 mm 1 H/broadband probe. Different fibers were cut and packed in 4 mm ZrO 2 rotors. Solid samples were spun at 12.5 kHz. The 51 V MAS NMR spectrum was acquired with a Hahn echo sequence (p/2-s-p-s acquisition) with a synchronized s and a 16-phase pulse program. The following acquisition parameters were used: spectral width of 1 MHz, pulse width of 1 ls, and a recycle time of 0.5 s. An accumulation of 115 200 transients was performed on the sample. Isotropic chemical shifts were referenced to pure VOCl 3 using a solution of 0.5 mol L -1 NaVO 3 (d iso = -578 ppm). A numerical simulation of the 51 V MAS spectrum was performed with the dmfit-QUA-SAR program [27]. This simulation included the effects of chemical shift anisotropy as well as first-and second-order quadrupolar interactions; both central and satellite transitions were considered. X-band ESR investigations were carried out with a Bruker ESP 300E spectrometer at ∼ 9.24 GHz and at both 298 and 77 K. The spectral width used was 2350-4350 G (1 G = 1 ×10 -4 T). Recently, white polymer light-emitting diodes (WPLEDs) have received particular attention because of their potential applications in backlight and full-color displays with color filters. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] The combination of white emission and color filters should simplify the fabrication process of fine-pixel large- COMMUNICATIONS 2974

New single‐polymer electroluminescent systems containing two individual emission species—polyfluorenes as a blue host and 2,1,3‐benzothiadiazole derivative units as an orange dopant on the main chain—have been designed and synthesized. The resulting single polymers are found to have highly efficient white electroluminescence with simultaneous blue (λmax = 421 nm/445 nm) and orange emission (λmax = 564 nm) from the corresponding emitting species. The influence of the photoluminescence (PL) efficiencies of both the blue and orange species on the electroluminescence (EL) efficiencies of white polymer light‐emitting diodes (PLEDs) based on the single‐polymer systems has been investigated. The introduction of the highly efficient 4,7‐bis(4‐(N‐phenyl‐N‐(4‐methylphenyl)amino)phenyl)‐2,1,3‐benzothiadiazole unit to the main chain of polyfluorene provides significant improvement in EL efficiency. For a single‐layer device fabricated in air (indium tin oxide/poly(3,4‐ethylenedioxythiophene): poly(styrene sulfonic acid/polymer/Ca/Al), pure‐white electroluminescence with Commission Internationale de l'Eclairage (CIE) coordinates of (0.35,0.32), maximum brightness of 12 300 cd m–2, luminance efficiency of 7.30 cd A–1, and power efficiency of 3.34 lm W–1 can be obtained. This device is approximately two times more efficient than that utilizing a single polyfluorene containing 1,8‐naphthalimide moieties, and shows remarkable improvement over the corresponding blend systems in terms of efficiency and color stability. Thermal treatment of the single‐layer device before cathode deposition leads to the further improvement of the device performance, with CIE coordinates of (0.35,0.34), turn‐on voltage of 3.5 V, luminance efficiency of 8.99 cd A–1, power efficiency of 5.75 lm W–1, external quantum efficiency of 3.8 %, and maximum brightness of 12 680 cd m–2. This performance is roughly comparable to that of white organic light‐emitting diodes (WOLEDs) with multilayer device structures and complicated fabrication processes.