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Degradation Mechanisms in Organic Light-Emitting Diodes with Polyethylenimine as a Solution-Processed Electron Injection Layer
被引:39
作者:
Stolz, Sebastian
[1
,2
]
Zhang, Yingjie
[3
,4
]
Lemmer, Uli
[1
,5
]
Hernandez-Sosa, Gerardo
[1
,2
]
Aziz, Hany
[3
,4
]
机构:
[1] Karlsruhe Inst Technol, Light Technol Inst, Engesserstr 13, D-76131 Karlsruhe, Germany
[2] InnovationLab, Speyerer Str 4, D-69115 Heidelberg, Germany
[3] Univ Waterloo, Dept Elect & Comp Engn, 200 Univ Ave West, Waterloo, ON N2L 3G1, Canada
[4] Univ Waterloo, Waterloo Inst Nanotechnol, 200 Univ Ave West, Waterloo, ON N2L 3G1, Canada
[5] Karlsruhe Inst Technol, Inst Microstruct Technol, Hermann von Helmholtz Pl 1, D-76344 Eggenstein Leopoldshafen, Germany
基金:
加拿大自然科学与工程研究理事会;
关键词:
OLEDs;
lifetime;
polyethylenimine;
electron injection layers;
solution-processing;
POLYMER SOLAR-CELLS;
SOLUBLE CONJUGATED POLYMERS;
GOLD NANOPARTICLES;
TRANSPORT LAYERS;
DEVICES;
EFFICIENT;
FLUORESCENCE;
POLYELECTROLYTES;
POLYFLUORENE;
INTERFACE;
D O I:
10.1021/acsami.6b15062
中图分类号:
TB3 [工程材料学];
学科分类号:
0805 ;
080502 ;
摘要:
In this work, we investigate the performance and operational stability of solution-processed organic light emitting diodes (OLEDs), which comprise polyethylenimine (PEI) as an electron injection layer (EIL). We show that the primary degradation mechanism in these OLEDs depends on the cathode metal that is used in contact with the EIL. In the case of Al, the deterioration in OLED performance during electrical driving is mainly caused by excitons which reach and subsequently degrade the emitter/PEI interface. In contrast, in the case of Ag, device performance degradation occurs due to an additional mechanism: hole accumulation at the emitter/PEI interface and a consequent drop in the emitter quantum yield. As a result, the operational lifetime of OLEDs that use PEI as EIL can vary significantly with the cathode material, and at a current density of 20 mA cm(-2), LT50 lifetimes of similar to 200 h and <10 h are obtained for Al and Ag, respectively. Finally, we show that the first degradation mechanism can be significantly slowed by using a mixture of PEI and ZnO nanoparticles as EIL. As a result, the operational lifetime of OLEDs with an Al cathode is increased to more than 1000 h, without adversely affecting device performance. This lifetime is significantly longer than that of a LiF/Al reference OLED.
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页码:2776 / 2785
页数:10
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