Effect of Hole Mobility Through Emissive Layer on Temporal Stability of Blue Organic Light-Emitting Diodes

• Published in: Advanced functional materials 2006-07, Vol.16 (11), p.1481-1487
• Main Authors: Culligan, S. W., Chen, A. C.-A., Wallace, J. U., Klubek, K. P., Tang, C. W., Chen, S. H.
• Format: Article
• Language: English
• Subjects: ANTHRACENE; Blue-light emitters; Charge transport; Charge-carrier mobility; ENGINEERING; FLUORENE; HOLE MOBILITY; LIGHT EMITTING DIODES; Light‐emitting diodes, organic; NAPHTHALENE; organic; Organic electronics; RECOMBINATION; SERVICE LIFE; STABILITY
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.200500785

Light‐emitting conjugated oligomers comprising anthracene, naphthalene, and fluorene units have been synthesized to investigate three configurations of blue organic light‐emitting diodes (OLEDs) that are designed to identify the origins of device instability. The transient OLED technique is employed to measure hole mobilities, which are found to be 3.1 × 10–4, 8.9 × 10–5, and 3.6 × 10–5 cm2 V–1 s–1 for three different blue‐light‐emitting model compounds with varying fluorene content. A higher hole mobility through the emissive layer results in a wider recombination zone, which, in turn, is responsible for a longer device lifetime and a lower drive voltage at the expense of luminance yield. Different blue‐light‐emitting conjugated oligomers (ADN, ANF, and ADF–see figure) have been synthesized in order to systematically study OLED instability. Measured using the transient‐OLED technique, hole mobility through the emissive layer is found to play a critical role: a higher hole mobility is responsible for a longer device lifetime and a lower drive voltage at the expense of luminance yield.