TY - JOUR
T1 - Efficient Charge Carrier Injection and Balance Achieved by Low Electrochemical Doping in Solution-Processed Polymer Light-Emitting Diodes
AU - Yan, Hao
AU - Limbu, Saurav
AU - Wang, Xuhua
AU - Nightingale, James
AU - Hamilton, Iain
AU - Wade, Jessica
AU - Kwon, Sooncheol
AU - Lee, Kwanghee
AU - Kim, Ji Seon
N1 - Publisher Copyright:
© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
PY - 2019/10/1
Y1 - 2019/10/1
N2 - Charge carrier injection and transport in polymer light-emitting diodes (PLEDs) is strongly limited by the energy level offset at organic/(in)organic interfaces and the mismatch in electron and hole mobilities. Herein, these limitations are overcome via electrochemical doping of a light-emitting polymer. Less than 1 wt% of doping agent is enough to effectively tune charge injection and balance and hence significantly improve PLED performance. For thick single-layer (1.2 µm) PLEDs, dramatic reductions in current and luminance turn-on voltages (VJ = 11.6 V from 20.0 V and VL = 12.7 V from 19.8 V with/without doping) accompanied by reduced efficiency roll-off are observed. For thinner (<100 nm) PLEDs, electrochemical doping removes a thickness dependence on VJ and VL, enabling homogeneous electroluminescence emission in large-area doped devices. Such efficient charge injection and balance properties achieved in doped PLEDs are attributed to a strong electrochemical interaction between the polymer and the doping agents, which is probed by in situ electric-field-dependent Raman spectroscopy combined with further electrical and energetic analysis. This approach to control charge injection and balance in solution-processed PLEDs by low electrochemical doping provides a simple yet feasible strategy for developing high-quality and efficient lighting applications that are fully compatible with printing technologies.
AB - Charge carrier injection and transport in polymer light-emitting diodes (PLEDs) is strongly limited by the energy level offset at organic/(in)organic interfaces and the mismatch in electron and hole mobilities. Herein, these limitations are overcome via electrochemical doping of a light-emitting polymer. Less than 1 wt% of doping agent is enough to effectively tune charge injection and balance and hence significantly improve PLED performance. For thick single-layer (1.2 µm) PLEDs, dramatic reductions in current and luminance turn-on voltages (VJ = 11.6 V from 20.0 V and VL = 12.7 V from 19.8 V with/without doping) accompanied by reduced efficiency roll-off are observed. For thinner (<100 nm) PLEDs, electrochemical doping removes a thickness dependence on VJ and VL, enabling homogeneous electroluminescence emission in large-area doped devices. Such efficient charge injection and balance properties achieved in doped PLEDs are attributed to a strong electrochemical interaction between the polymer and the doping agents, which is probed by in situ electric-field-dependent Raman spectroscopy combined with further electrical and energetic analysis. This approach to control charge injection and balance in solution-processed PLEDs by low electrochemical doping provides a simple yet feasible strategy for developing high-quality and efficient lighting applications that are fully compatible with printing technologies.
KW - charge injection and balance
KW - electrochemical doping
KW - organic light-emitting diodes
KW - organic semiconductors
KW - solid-state ionic liquids
UR - http://www.scopus.com/inward/record.url?scp=85070780076&partnerID=8YFLogxK
U2 - 10.1002/adfm.201904092
DO - 10.1002/adfm.201904092
M3 - Article
AN - SCOPUS:85070780076
SN - 1616-301X
VL - 29
JO - Advanced Functional Materials
JF - Advanced Functional Materials
IS - 40
M1 - 1904092
ER -