TY - GEN
T1 - Carrier injection and bipolar transport in NPB for single-layers OLEDs
AU - Tse, S. C.
AU - Tsung, K. K.
AU - So, S. K.
N1 - Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
PY - 2007
Y1 - 2007
N2 - We studied the carrier injection and transporting properties of N,N′-diphenyl-N,N′-bis(1-naphthyl)(1,1′-biphenyl)-4,4'diamine (NPB), a common hole transporter for organic light-emitting diodes (OLEDs). NPB was found to possess significant electron mobility from time-of-flight (TOF) measurement. With bipolar transporting ability, NPB was used to fabricate single-layer devices with a configuration of ITO/ PEDOT:PSS/ NPB/ Ca/ Ag. PEDOT:PSS was demonstrated to form a quasi-Ohmic contact to NPB by admittance spectroscopy (AS) and dark-injection space-charge-limited current (DISCLC) measurements. From current-voltage (JV) characteristics, single-layer NPB devices exhibited a bulk-limited hole current in low-voltage region. Electron injection was clearly observed at a turn-on voltage of about 4V, which coincided with the luminance-voltage measurement. In order to confine the recombination zone, dye-doped NPB layer was inserted into single-layer devices. This intentional doping technique made a notable improvement in current efficiency. The mechanisms of the doped devices were also addressed.
AB - We studied the carrier injection and transporting properties of N,N′-diphenyl-N,N′-bis(1-naphthyl)(1,1′-biphenyl)-4,4'diamine (NPB), a common hole transporter for organic light-emitting diodes (OLEDs). NPB was found to possess significant electron mobility from time-of-flight (TOF) measurement. With bipolar transporting ability, NPB was used to fabricate single-layer devices with a configuration of ITO/ PEDOT:PSS/ NPB/ Ca/ Ag. PEDOT:PSS was demonstrated to form a quasi-Ohmic contact to NPB by admittance spectroscopy (AS) and dark-injection space-charge-limited current (DISCLC) measurements. From current-voltage (JV) characteristics, single-layer NPB devices exhibited a bulk-limited hole current in low-voltage region. Electron injection was clearly observed at a turn-on voltage of about 4V, which coincided with the luminance-voltage measurement. In order to confine the recombination zone, dye-doped NPB layer was inserted into single-layer devices. This intentional doping technique made a notable improvement in current efficiency. The mechanisms of the doped devices were also addressed.
KW - Admittance spectroscopy
KW - Bipolar transport
KW - Charge injection
KW - Organic light-emitting diodes
UR - http://www.scopus.com/inward/record.url?scp=42149116899&partnerID=8YFLogxK
U2 - 10.1117/12.733775
DO - 10.1117/12.733775
M3 - Conference proceeding
AN - SCOPUS:42149116899
SN - 9780819468031
T3 - Proceedings of SPIE - The International Society for Optical Engineering
BT - Organic Light Emitting Materials and Devices XI
T2 - Organic Light Emitting Materials and Devices XI
Y2 - 26 August 2007 through 29 August 2007
ER -