TY - JOUR
T1 - On the use and influence of electron-blocking interlayers in polymer light-emitting diodes
AU - Jin, Rui
AU - Levermore, Peter A.
AU - Huang, Jingsong
AU - Wang, Xuhua
AU - Bradley, Donal D.C.
AU - DeMello, John C.
N1 - Generated from Scopus record by KAUST IRTS on 2019-11-27
PY - 2009/5/5
Y1 - 2009/5/5
N2 - We report current-voltage-luminance and electromodulation measurements on a series of polymer light-emitting diodes, using indium tin oxide (ITO) coated with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the anode, poly(9,9-dioctylfluorene-alt-N-(4-butylphenyl)-diphenylamine) (TFB) as an optional anodic interlayer material, poly(9,9-dioctylfluorene-alt-bithiophene) (F8T2) as the emissive layer, and either aluminium or (aluminium-capped) calcium as the cathode. Four device structures were investigated: ITO/PEDOT:PSS/F8T2/ Al, ITO/PEDOT:PSS/F8T2/Ca, ITO/PEDOT:PSS/TFB/F8T2/Al, and ITO/PEDOT:PSS/TFB/ F8T2/Ca. The devices with interlayers had substantially higher luminance and power efficiencies than their interlayer-free counterparts- a fact we attribute to the energy and mobility barriers that exist at the TFB-F8T2 interface. These barriers play two crucial roles in enhancing device efficiency: firstly, they cause the most easily injected charge carrier to accumulate at the TFB-F8T2 interface until efficient injection of the opposite carrier type becomes favourable; and, secondly, they inhibit electron and hole 'seepage' across the interface, thereby reducing leakage currents. The beneficial influence of these two effects is most marked for the interlayer-containing Al device which, in spite of a sizeable 0.9 eV barrier to electron injection at the cathode, exhibited surprisingly high luminous and power efficiencies of 2.4 cd A -1 and 1.1 lm W-1 at an arbitrary reference luminance of 2500 cd m-2. This compares with peak values of just 0.11 cd A -1 and 0.07 lm W-1 at 25 cd m-2 for the equivalent interlayer-free device (falling to 0.058 cd A-1 and 0.025 lm W-1 at 100 cd m-2). The interlayer-containing Ca device had luminous and power efficiencies of 3.5 cd A-1 and 2.9 lm W -1 at 2500 cd m-2 compared to 1.1 cd A-1 and 0.7 lm W-1 for the equivalent interlayer-free device at 2500 cd m-2. © 2009 the Owner Societies.
AB - We report current-voltage-luminance and electromodulation measurements on a series of polymer light-emitting diodes, using indium tin oxide (ITO) coated with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the anode, poly(9,9-dioctylfluorene-alt-N-(4-butylphenyl)-diphenylamine) (TFB) as an optional anodic interlayer material, poly(9,9-dioctylfluorene-alt-bithiophene) (F8T2) as the emissive layer, and either aluminium or (aluminium-capped) calcium as the cathode. Four device structures were investigated: ITO/PEDOT:PSS/F8T2/ Al, ITO/PEDOT:PSS/F8T2/Ca, ITO/PEDOT:PSS/TFB/F8T2/Al, and ITO/PEDOT:PSS/TFB/ F8T2/Ca. The devices with interlayers had substantially higher luminance and power efficiencies than their interlayer-free counterparts- a fact we attribute to the energy and mobility barriers that exist at the TFB-F8T2 interface. These barriers play two crucial roles in enhancing device efficiency: firstly, they cause the most easily injected charge carrier to accumulate at the TFB-F8T2 interface until efficient injection of the opposite carrier type becomes favourable; and, secondly, they inhibit electron and hole 'seepage' across the interface, thereby reducing leakage currents. The beneficial influence of these two effects is most marked for the interlayer-containing Al device which, in spite of a sizeable 0.9 eV barrier to electron injection at the cathode, exhibited surprisingly high luminous and power efficiencies of 2.4 cd A -1 and 1.1 lm W-1 at an arbitrary reference luminance of 2500 cd m-2. This compares with peak values of just 0.11 cd A -1 and 0.07 lm W-1 at 25 cd m-2 for the equivalent interlayer-free device (falling to 0.058 cd A-1 and 0.025 lm W-1 at 100 cd m-2). The interlayer-containing Ca device had luminous and power efficiencies of 3.5 cd A-1 and 2.9 lm W -1 at 2500 cd m-2 compared to 1.1 cd A-1 and 0.7 lm W-1 for the equivalent interlayer-free device at 2500 cd m-2. © 2009 the Owner Societies.
UR - http://xlink.rsc.org/?DOI=b819200f
UR - http://www.scopus.com/inward/record.url?scp=65349140065&partnerID=8YFLogxK
U2 - 10.1039/b819200f
DO - 10.1039/b819200f
M3 - Article
SN - 1463-9076
VL - 11
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
IS - 18
ER -