Approaching Charge Balance in Organic Light-Emitting Diodes by Tuning Charge Injection Barriers with Mixed Monolayers

Yu, Szu-Yen; Huang, Ding‐Chi; Wu, Kun-Yang; Tao, Yu‐Tai

doi:10.1021/la2036423

Cited by 35 publications

(30 citation statements)

References 63 publications

(42 reference statements)

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“…In this way, charge injection barriers can be controlled, with consequent effects on device performance . Multicomponent monolayers can offer a higher flexibility in tuning the work function if the molecular ratio is varied, and have been studied for this reason for some time . Most of these multi‐component layer studies use long, alkyl based molecules such as thiols, and the molecular monolayer is used as a buffer layer for deposition of a further organic layer atop.…”

Section: Binary Layers On Metal Surfacesmentioning

confidence: 99%

Multi‐Component Organic Layers on Metal Substrates

et al. 2015

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Increasingly high hopes are being placed on organic semiconductors for a variety of applications. Progress along these lines, however, requires the design and growth of increasingly complex systems with well-defined structural and electronic properties. These issues have been studied and reviewed extensively in single-component layers, but the focus is gradually shifting towards more complex and functional multi-component assemblies such as donor-acceptor networks. These blends show different properties from those of the corresponding single-component layers, and the understanding on how these properties depend on the different supramolecular environment of multi-component assemblies is crucial for the advancement of organic devices. Here, our understanding of two-dimensional multi-component layers on solid substrates is reviewed. Regarding the structure, the driving forces behind the self-assembly of these systems are described. Regarding the electronic properties, recent insights into how these are affected as the molecule's supramolecular environment changes are explained. Key information for the design and controlled growth of complex, functional multicomponent structures by self-assembly is summarized.

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Section: Binary Layers On Metal Surfacesmentioning

confidence: 99%

Multi‐Component Organic Layers on Metal Substrates

et al. 2015

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“…In order to improve the interface characteristics, the insertion of a buffer/injection layer between anode and hole transport layer (HTL) is one of the simple and effective methods to improve the device performances. An organic buffer layer, such as copper phthalocyanine (CuPc), 2 starburst amines (m-MTDATA), 3 poly (3,4-ethylene dioxythiophene) (PEDOT), 4 CHF 3 , 5 or self-assembled mono-layers (SAMs), 6 normally brings an energy-band alignment between the HTL and the anode, which lowers the energy barrier, reduces the turn-on voltage and increases the OLEDs lifetime. Inorganic insulator buffer layers, such as LiF, 7-9 Al 2 O 3 , 10 SiO 2 , 11 H f O x , 12 MoO 3 , 13 and WO 2.5 , 14 were also reported in literature, some of which showed higher current efficiency 9,11,12 and others showed higher power efficiency.…”

Section: Introductionmentioning

confidence: 99%

Performance improvement of organic light emitting diode with aluminum oxide buffer layer for anode modification

Zhuang

Tongay

et al. 2013

Journal of Applied Physics

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A thin Al 2 O 3 insulating buffer layer deposited on indium tin oxide (ITO) anode by atomic layer deposition has been investigated for organic light-emitting diodes (OLEDs). With an optimal thickness of 1.4 nm and low density of structural defects of the Al 2 O 3 film, the OLEDs current efficiency and power efficiency were simultaneously improved by 12.5% and 23.4%, respectively. The improvements in both current and power efficiency mean lower energy loss during holes injection process and better balanced charge injection. To understand the mechanism behind the enhanced performance of OLED by the buffer layer, a series of Al 2 O 3 films of different thicknesses were deposited on ITO anode and characterized. The roughness, sheet resistance, and surface potential (E F 0 ) of the Al 2 O 3 modified ITO were characterized. Also, the properties of Al 2 O 3 films were investigated at the device level. It is believed that the block of holes injection by the Al 2 O 3 buffer layer makes more balanced carrier density in the emitting layer, thus enhances the current efficiency. Although less number of holes are injected into OLED due to the Al 2 O 3 buffer layer, quantum tunneling through the ultra-thin buffer layer play an important role in contributing to the holes injection, which avoids crossing the interface barrier, resulting in less energy consumed and power efficiency enhanced. V C 2013 AIP Publishing LLC. [http://dx.

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“…By contrast, in the UFNP-device, the electron injects into the EML at $3.0 V, which is close to the voltage for the hole injection and achieves a better charge balance in HFSO for efficient radiative recombination. 19 The reduction of V t ($0.3 V) is higher than the energy discrepancy ($0.2 eV) of conduction band edges of UFNPs and NSNPs, probably with the enhancement of Auger-assisted energy up-conversion process suggested by Qian et al 20 Also, by reducing the leakage current observed in the NSNP-device, the UFNP-device can achieve higher L max (7300 cd m À2 ) and similar current efficiency (h c ) (1.13 cd A À1 , see Fig. 6(b)) compared to those (4300 cd m À2 and 1.12 cd A À1 ) of the counterpart with Ca/Al cathodes in our previous study.…”

Section: Resultsmentioning

confidence: 99%