Efficient spin-coated small molecule OLEDs (SMOLEDs) [Adv. Mater. 23 , 3590 (2011)], highly efficient ITO-free SMOLEDs [Adv. Mater. 24 , 4337 (2012)], and recent advances in the OLED-based chemical and biological sensors [Anal. Chim. Acta 778 , 70 (2013)] are described. The spin-coated SMOLEDs' structure was glass/ITO/(3,4-ethylenedioxy thiophene):poly(styrenesulfonate) (PEDOT:PSS)/CBP:TPD:PBD:Ir(mppy)3/BPhen/LiF/Al (CBP is 4,4'-bis(9-carbazolyl)-biphenyl, TPD is N,N'-diphenyl-N,N'-bis(3-methyl-phenyl)-[l,l'biphenyl]-4,4'-diamine, PBD is 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole, Ir(mppy)3 is tris[2-(p-tolyl)pyridine] iridium(III), and BPhen is 4,7-diphenyl-1,10-phenanthroline). They yielded maximal efficiencies of 60 lm/W and 69 cd/A, vs 22 lm/W and 35 cd/A for similar devices where poly(N-vinyl carbazole) (PVK) replaced the CBP; they were obtained with no outcoupling enhancing structures. Highly efficient ITO-free SMOLEDs were fabricated on highly conductive multilayered PEDOT:PSS. The SMOLEDs' structure was glass/PEDOT:PSS/MoO3/MoO3 (10 wt.%):NPD/NPD/Ir(ppy)3 (6 wt.%):CBP/BPhen/LiF/Al (NPD is N,N'-diphenyl-N,N'-bis(1-naphthyl-phenyl)-1,1'-biphenyl-4,4'-diamine and Ir(ppy)3 is tris(2-phenylpyridine) iridium(III)). The devices exhibited a peak power efficiency of 118 lm/W, or 44% higher than that of similar ITO-based SMOLEDs, with no outcoupling enhancing structures. Ab initio modeling indicates that the improved device performance is due to the higher light outcoupling from the PEDOT:PSS-based devices. Finally, key issues in using OLEDs as excitation sources in structurally integrated photoluminescence (PL)-based sensors are the low ~20% forward light outcoupling, the OLEDs' broad electroluminescence (EL) bands that interferes with the analyte-sensitive PL, and the long-lived remnant EL that follows an EL pulse. These issues hinder designing compact miniaturizable sensors that are devoid of optical filters and couplers. We address these shortcomings by introducing easy-to-employ multiple approaches for outcoupling improvement, PL enhancement, and background EL reduction leading to novel, compact all-organic device architectures demonstrated for simultaneous monitoring of oxygen and pH. The sensor comprises simply-fabricated, directionally-emitting, narrower-band, multicolor microcavity OLED excitation and small molecule- and polymer-based organic photodetectors (OPDs) with a more selective spectral response.

Recent advances in spin-coated small molecule OLEDs, ITO-free OLEDs, and OLED-based chemical and biological sensors

247th National Meeting (2014)

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