Abstract
Flexible white top-emitting organic light-emitting diodes (WTEOLEDs) with red and blue phosphorescent dual-emitting layers were fabricated onto polyethylene terephthalate (PET) substrates. By inserting a 2-nm thin tris(phenypyrazole)iridium between the red and the blue emitters as an electron/exciton blocking layer, significant improvements on luminous efficiency and color stability were observed, reaching 9.9cd/A (3.74lm/W) and a small chromaticity change of (0.019, 0.011) in a wide luminance range of 80–5160cd/m2. The origin on color stability was explored by analyzing the electroluminescent spectra, the time-resolved transient photoluminescence decay lifetimes of phosphors, and the tunneling phenomenon. In addition, mechanical bending lifetimes in WTEOLEDs with spin-coatedpolymethylmethacrylate (PMMA) and thermally evaporated MoOx onto the PETs were respectively measured, where PMMA or MoOx is used as a surface planarization layer. Analysis indicates that the poorer lifetime of PMMA-modified WTEOLED than the MoOx-modified ones is mainly due to the low surface energy of PMMA.
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