TY - JOUR
T1 - n-Doping of a Low-Electron-Affinity Polymer Used as an Electron-Transport Layer in Organic Light-Emitting Diodes
AU - Smith, Hannah L.
AU - Dull, Jordan T.
AU - Longhi, Elena
AU - Barlow, Stephen
AU - Rand, Barry P.
AU - Marder, Seth R.
AU - Kahn, Antoine
N1 - Funding Information:
This work was supported in part by a grant of the National Science Foundation (DMR‐1807797) (H.L.S., E.L., S.B., B.P.R., S.R.M., A.K.), by a National Science Foundation Graduate Research Fellowship (DGE‐1656466) (H.L.S.), and by a grant from the Department of Energy Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award #DE‐SC0012458 (J.T.D., B.P.R., A.K.). The authors acknowledge the use of the Cary 5000 UV–vis–NIR spectrometer in the Princeton's Imaging and Analysis Center, which is partially supported by the Princeton Center for Complex Materials, a National Science Foundation (NSF)‐MRSEC program (DMR‐1420541).
Funding Information:
This work was supported in part by a grant of the National Science Foundation (DMR-1807797) (H.L.S., E.L., S.B., B.P.R., S.R.M., A.K.), by a National Science Foundation Graduate Research Fellowship (DGE-1656466) (H.L.S.), and by a grant from the Department of Energy Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award #DE-SC0012458 (J.T.D., B.P.R., A.K.). The authors acknowledge the use of the Cary 5000 UV?vis?NIR spectrometer in the Princeton's Imaging and Analysis Center, which is partially supported by the Princeton Center for Complex Materials, a National Science Foundation (NSF)-MRSEC program (DMR-1420541).
Publisher Copyright:
© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
PY - 2020/4/1
Y1 - 2020/4/1
N2 - n-Doping electron-transport layers (ETLs) increases their conductivity and improves electron injection into organic light-emitting diodes (OLEDs). Because of the low electron affinity and large bandgaps of ETLs used in green and blue OLEDs, n-doping has been notoriously more difficult for these materials. In this work, n-doping of the polymer poly[(9,9-dioctylfluorene-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,7-diyl)] (F8BT) is demonstrated via solution processing, using the air-stable n-dopant (pentamethylcyclopentadienyl)(1,3,5-trimethylbenzene)ruthenium dimer [RuCp*Mes]2. Undoped and doped F8BT films are characterized using ultraviolet and inverse photoelectron spectroscopy. The ionization energy and electron affinity of the undoped F8BT are found to be 5.8 and 2.8 eV, respectively. Upon doping F8BT with [RuCp*Mes]2, the Fermi level shifts to within 0.25 eV of the F8BT lowest unoccupied molecular orbital, which is indicative of n-doping. Conductivity measurements reveal a four orders of magnitude increase in the conductivity upon doping and irradiation with ultraviolet light. The [RuCp*Mes]2-doped F8BT films are incorporated as an ETL into phosphorescent green OLEDs, and the luminance is improved by three orders of magnitude when compared to identical devices with an undoped F8BT ETL.
AB - n-Doping electron-transport layers (ETLs) increases their conductivity and improves electron injection into organic light-emitting diodes (OLEDs). Because of the low electron affinity and large bandgaps of ETLs used in green and blue OLEDs, n-doping has been notoriously more difficult for these materials. In this work, n-doping of the polymer poly[(9,9-dioctylfluorene-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,7-diyl)] (F8BT) is demonstrated via solution processing, using the air-stable n-dopant (pentamethylcyclopentadienyl)(1,3,5-trimethylbenzene)ruthenium dimer [RuCp*Mes]2. Undoped and doped F8BT films are characterized using ultraviolet and inverse photoelectron spectroscopy. The ionization energy and electron affinity of the undoped F8BT are found to be 5.8 and 2.8 eV, respectively. Upon doping F8BT with [RuCp*Mes]2, the Fermi level shifts to within 0.25 eV of the F8BT lowest unoccupied molecular orbital, which is indicative of n-doping. Conductivity measurements reveal a four orders of magnitude increase in the conductivity upon doping and irradiation with ultraviolet light. The [RuCp*Mes]2-doped F8BT films are incorporated as an ETL into phosphorescent green OLEDs, and the luminance is improved by three orders of magnitude when compared to identical devices with an undoped F8BT ETL.
KW - electron-transport layers
KW - low-electron-affinity polymers n-doping
KW - organic light-emitting diodes
KW - organic semiconductors
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U2 - 10.1002/adfm.202000328
DO - 10.1002/adfm.202000328
M3 - Article
AN - SCOPUS:85080151843
SN - 1616-301X
VL - 30
JO - Advanced Functional Materials
JF - Advanced Functional Materials
IS - 17
M1 - 2000328
ER -