Improving efficiency by balancing carrier transport in poly(9,9-dioctylfluorene) light-emitting diodes using tetraphenylporphyrin as a hole-trapping, emissive dopant

Campbell, Alasdair J.; Bradley, Donal D. C.; Virgili, Tersilla; Lidzey, David G.; Antoniadis, Homer
December 2001
Applied Physics Letters;12/3/2001, Vol. 79 Issue 23, p3872
Academic Journal
Unbalanced carrier transport is known to strongly affect the efficiency of polymer light-emitting diodes. Here, we report the results of time-of-flight (TOF), current density–voltage, and electroluminescence (EL) quantum efficiency measurements on single-layer poly(9,9-dioctylfluorene) (PFO) devices doped with the red-emitter tetraphenylporphyrin (TPP). TOF shows that PFO is a unipolar conductor, with hole transport much better than electron transport. At a field of 5×10[sup 5] V/cm, a nondispersive hole mobility of 4×10[sup -5]–5×10[sup -4] cm[sup 2]/V s, dependent on sample morphology, is obtained. Upon the addition of 5% by weight TPP, hole transport becomes as highly dispersive as electron transport, having no measurable average mobility. This results in a decrease in the current for a given applied bias but an increase in the external EL quantum efficiency. TPP acts as a strong hole trap, reducing the dominant hole current and producing more balanced carrier transport. At TPP concentrations above 6%, the device characteristics start to revert to those found at lower TPP concentrations. This is due to the onset of efficient hole transport between the dopant molecules that reestablishes a transport imbalance. © 2001 American Institute of Physics.


Related Articles

  • Dispersive electron transport in an electroluminescent polyfluorene copolymer measured by the current integration time-of-flight method. Campbell, Alasdair J.; Bradley, Donal D. C.; Antoniadis, Homer // Applied Physics Letters;10/1/2001, Vol. 79 Issue 14, p2133 

    Here, we report results of both traditional current mode and current integration mode time-of-flight (TOF) measurements on the electroluminescent polyfluorene copolymer poly(9,9-dioctylfluorene-co-benzothiadiazole) (BT). Current mode TOF shows a strong but dispersive electron transport signal....

  • Study of organic light emitting devices with a 5,6,11,12-tetraphenylnaphthacene (rubrene)-doped hole transport layer. Aziz, Hany; Popovic, Zoran D. // Applied Physics Letters;3/25/2002, Vol. 80 Issue 12, p2180 

    We investigated the stability of an organic light emitting device (OLED) with structure of indiumtin-oxide (ITO) anode/N,N'-di(naphthalene-1-yl)-N,N'-diphenyl-benzidine hole transport layer (HTL)/tris(8-hydroxyquinoline) aluminum (AlQ[sub 3]) electron transport layer/Mg:Ag cathode, in which...

  • Bright-blue electroluminescence from a silyl-substituted ter-(phenylene-vinylene) derivative. Zhiquiang Gao; Lee, C.S.; Bello, I.; Lee, S.T.; Ruey-Ming Chen; Tien-Yau Luh; Shi, J.; Tang, C.W. // Applied Physics Letters;2/8/1999, Vol. 74 Issue 6, p865 

    Describes a bright-blue electroluminescent device fabricated using an emissive dopant and an electron-transporting host. Trimer which functioned as the host and electron transporter; Device structure; Current density of the emission; Current efficiency of the device.

  • High-field transport and electroluminescence in ZnS phosphor layers. Dur, Manfred; Goodnick, Stephen M.; Pennathur, Shankar S.; Wager, John F.; Reigrotzki, Martin; Redmer, Ronald // Journal of Applied Physics;3/15/1998, Vol. 83 Issue 6, p3176 

    Focuses on the performance of the high-field electron transport in the zinc sulphur (ZnS) phosphor layer of an alternating-current thin-film electroluminescent device. What the simulation included; Exhibition of the computed impact excitation yield for carriers transiting the phosphor layer;...

  • Electron drift mobility in polystyrene doped with bispyrazolopyridine derivatives. Tameev, A. R.; He, Z.; Milburn, G. H. W.; Kozlov, A. A.; Vannikov, A. V.; Puchala, A.; Rasala, D. // Applied Physics Letters;8/5/2002, Vol. 81 Issue 6, p969 

    Electron transport properties of bispyrazolopyridine derivatives have been studied using a conventional time-of-flight method. A field dependent electron drift mobility, in the range of 4 × 10[sup -7]-2 × 10[sup -5] cm²/(V s) at an electric field of (0.6-7.0) × l0[sup 5] V/cm, has...

  • Carrier deep-trapping mobility-lifetime products in poly(p-phenylene vinylene). Antoniadis, H.; Abkowitz, M.A. // Applied Physics Letters;10/17/1994, Vol. 65 Issue 16, p2030 

    Details the transport limitation of a single layer poly(p-phenylene vinylene) electroluminescence device. Quantification of transport range of electrons and holes; Deduction of deep-trapping mobility-lifetime products; Execution of space-charged-limited current measurement in bilayer devices.

  • Electroluminescence from trap-limited current transport in vacuum deposited organic light.... Burrows, P.E.; Forrest, S.R. // Applied Physics Letters;4/25/1994, Vol. 64 Issue 17, p2285 

    Investigates the current transport and electroluminescence mechanisms in vacuum deposited light emitting devices. Composition of the light emitting devices; Dependence of current-voltage and luminescence efficiency on layer thickness and hole transport layer composition; Factors attributed to...

  • Tuning of the emission color of organic electroluminescent devices by exciplex formation at the organic solid interface. Ogawa, H.; Okuda, R.; Shirota, Y. // Applied Physics A: Materials Science & Processing;1998, Vol. 67 Issue 5, p599 

    Abstract. Exciplex formation at the organic solid interface and its application to the tuning of emission color in organic electroluminescent devices have been investigated. The bilayer organic electroluminescent devices composed of an electron-transporting amorphous molecular material,...

  • Infrared electroluminescence from an organic ionic dye containing no rare-earth ions. Suzuki, Hiroyuki // Applied Physics Letters;5/6/2002, Vol. 80 Issue 18, p3256 

    This paper reports the electroluminescence (EL) characteristics of a single-layer light-emitting diode (LED) with an organic functional layer, which is composed of an organic ionic emissive dye, IR1051, an electron transporting material, 2-(4-biphenylyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole, and...


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics