TY - JOUR
T1 - Charge trapping and scattering by extrinsic gas dopants in tris(8-hydroxyquinoline) aluminum (Alq3)
AU - Fong, H. H.
AU - So, S.K.
N1 - Funding information:
The authors would like to thank the support by Research Committee of Hong Kong Baptist University (FRG/03-04/I-06) and the Research Grant Council of Hong Kong.
Publisher copyright:
© Materials Research Society 2004
PY - 2004/12
Y1 - 2004/12
N2 - The effects of various ambient gases (N2, O2, H2O) to the electron mobility of tris(8-hydroxyquinoline) aluminum, Alq3, were examined. For a clean Alq3, the electron transport is non-dispersive and essentially trap-free as revealed by optical time-of-flight measurements. At 295K, the electron mobility (μℓ) spans the range 0.2-1×10-6 cm2V-1s-1 when the field varies from 0.4-0.9 MV cm-1. Exposing the sample to oxygen dosages in the range 1-100 Torr-s does not cause any noticeable changes in μℓ. The effect of oxygen on μℓ, can be observed only at much higher oxygen dosages (>105 Torr.s). In contrast, exposing pristine Alq3 to moisture of same dosages causes a gradual reduction in μℓ by a factor of 4. It is proposed that oxygen diffuses into Alq 3 during exposure and subsequently acts as charge scattering centers for externally injected free electrons. On the other hand, water induces charge traps at high dosages. Moisture control appears to be the most critical factor for the long-term operation of Alq3-based organic light-emitting diodes.
AB - The effects of various ambient gases (N2, O2, H2O) to the electron mobility of tris(8-hydroxyquinoline) aluminum, Alq3, were examined. For a clean Alq3, the electron transport is non-dispersive and essentially trap-free as revealed by optical time-of-flight measurements. At 295K, the electron mobility (μℓ) spans the range 0.2-1×10-6 cm2V-1s-1 when the field varies from 0.4-0.9 MV cm-1. Exposing the sample to oxygen dosages in the range 1-100 Torr-s does not cause any noticeable changes in μℓ. The effect of oxygen on μℓ, can be observed only at much higher oxygen dosages (>105 Torr.s). In contrast, exposing pristine Alq3 to moisture of same dosages causes a gradual reduction in μℓ by a factor of 4. It is proposed that oxygen diffuses into Alq 3 during exposure and subsequently acts as charge scattering centers for externally injected free electrons. On the other hand, water induces charge traps at high dosages. Moisture control appears to be the most critical factor for the long-term operation of Alq3-based organic light-emitting diodes.
UR - https://www.cambridge.org/core/journals/mrs-online-proceedings-library-archive/article/abs/charge-trapping-and-scattering-by-extrinsic-gas-dopants-in-tris8hydroxyquinoline-aluminum-alq3/78FFD2B7B46AE7F92AB91C85861F3C1A#
UR - http://www.scopus.com/inward/record.url?scp=12844271106&partnerID=8YFLogxK
U2 - 10.1557/proc-814-i10.18
DO - 10.1557/proc-814-i10.18
M3 - Conference article
AN - SCOPUS:12844271106
SN - 1946-4274
VL - 814
SP - 42
EP - 46
JO - MRS Online Proceedings Library
JF - MRS Online Proceedings Library
T2 - Flexible Electronics 2004 - Materials and Device Technology
Y2 - 13 April 2004 through 16 April 2004
ER -