12 January 2005 White polymer light-emitting diodes with bilayer structure
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White polymer light-emitting diodes (WPLEDs) with bilayer structure were fabricated by spin coating method. The device structure used here is ITO/PEDOT:PSS/blend1/blend2/Ba/Al, where blend1 consists of poly(N-vinylcarbazole) (PVK) and copolymer of 9,9-diotylfluorene and 4,7-di(3-hexyl-thien-2-yl)-2,1,3-benzothiadiazole (PFO-DHTBT), and blend2 is the blend of polyhedral oligomeric silsesquioxane-terminated poly(9,9-dioctylfluorene) (PFO-poss) and phenyl-substituted PPV derivative (P-PPV). The copolymer PFO-DHTBT emits red light. The blend2 gives off both green and blue emission bands in electroluminescence (EL) spectrum. the relative intensity of the bands depends on the blend ratios. The EL spectrum of the device can be controlled by respectively adjusting the weight ratios in the blend1 and blend2, thickness as well. At the weight ratios of 100:3 (PVK:PFO-DHTBT) in blend1 and 100:1 (PFO-poss: P-PPV) in blend2, and with keeping the thickness of the two blend films to be 40nm, the white fluorescent light emission with Commission International De L'Eclairage (CIE) coordinates of (0.33, 0.32) is achieved in a large voltage range, the maximal quantum and luminance efficiencies of 3% (ph/eh) and 4.4cd/A are obtained at 6.1V, and the maximal luminance is 6300cd/m2 at 10V.
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Yunhua Xu, Junbiao Peng, Yueqi Mo, Qiong Hou, Yong Cao, "White polymer light-emitting diodes with bilayer structure", Proc. SPIE 5632, Light-Emitting Diode Materials and Devices, (12 January 2005); doi: 10.1117/12.588294; https://doi.org/10.1117/12.588294

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