Light manipulation in organic light‐emitting devices by integrating micro/nano patterns

Feng, Jing; Liu, Yuefeng; Bi, Yan‐Gang; Sun, Hong–Bo

doi:10.1002/lpor.201600145

Cited by 57 publications

(27 citation statements)

References 210 publications

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“…Light extraction efficiency has always been the focus and keypoint of the FOLEDs due to the significant radiation loss in conventional OLEDs. About 80% of internally generated photons are trapped in different forms including surface plasmon polaritons (SPPs) mode associated with the interface between metal electrode and organic, the substrate mode owing to the total internal reflection at the substrate/air interface, waveguide (WG) modes in ITO anode and organic layers . Thus, light extraction efficiency of the conventional OLEDs is commonly less than 20%.…”

Section: Efficiency Improvement Of Flexible Organic Light‐emitting Dementioning

confidence: 99%

“…In terms of fabrication techniques, Feng et al have discussed that integrating the micro and nanostructures into the conventional OLEDs in detail in the other review . Holographic lithography, nanoimprint lithography, mold transfer process, colloidal lithography, E‐beam lithography, and spontaneously formed random patterns due to the anisotropy of materials are all effective techniques.…”

Section: Efficiency Improvement Of Flexible Organic Light‐emitting Dementioning

confidence: 99%

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Recent Developments in Flexible Organic Light‐Emitting Devices

Liu

Feng

et al. 2018

Adv Materials Technologies

Self Cite

117

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wearable displays, and conceptual lighting panels. In addition, besides the excellent designs, a flexible OLED (FOLED) [7, has several other advantages, the displays and lighting panels are thinner, lighter, more cost effective, shatterproof, and durable compared to glass or silicon based OLEDs. They are impact resistance and less prone to break than glass. At present, both flexible displays and lighting panels are being mass produced (Samsung and LG on displays, LG and Konica Minolta on lighting). FOLEDs are becoming most promising and popular next-generation display technology in consumer electronics and lighting panels.In order to develop the FOLEDs and realize their practical application, many great efforts have been conducted. The key components of the FOLEDs are flexible substrate, bottom and top electrode, organic functional layers, encapsulation layer, and optional light extraction layers. Differed from conventional OLEDs on rigid glass or silicon substrate, FOLEDs are fabricated on flexible substrates. Up to now, metal foil, flexible glass, and plastic film have been commonly used as flexible substrates for FOLEDs. On the other hand, actual fabric materials, natural silk fibroin films, bacterial cellulose, and rubbery poly (urethane acrylate) have also been developed to achieve the requirements of wearable and stretchable displays. The electrode is also very important for FOLEDs. Compared with the top electrode, more research has been conducted on the bottom electrode because its surface roughness, conductivity, and transmittance for bottom emitting OLEDs play a key role in the performance of FOLEDs. As conventional indiumtin-oxide (ITO) is not suitable for flexible devices as it is brittle, many great alternatives such as thin metal film, conducting polymer, dielectric-metal-dielectric (DMD) multilayers, metal nanowires, graphene, carbon nanotubes (CNTs), and their compound have been studied. It should be mentioned that the performance of organic layers has almost no difference with rigid OLEDs because of their inherent excellent ductility and identical working mechanism. Moreover, for practical and commercial applications, stability and efficiency are two factors of crucial importance. As a consequence, the encapsulation technique and light extraction of FOLEDs are also two research hotspots in recent years. This review will summarize the key components, discuss the method of implementation, highlight the recent research progresses, and conclude the challenges and prospects of FOLEDs. demand for display technology in consumer electronics and lighting panels increases, thin, light, high-quality, and more cost-effective light-emitting devices are required. Organic light-emitting devices (OLEDs), satisfying the criteria exactly, have been considered the most promising next-generation display and lighting technique. In particular, an OLED based on flexible substrate enables the device to be applied to curved displays, electronic newspapers, wearable displays, and conceptual lighting panels, has been alwa...

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Section: Efficiency Improvement Of Flexible Organic Light‐emitting Dementioning

confidence: 99%

Section: Efficiency Improvement Of Flexible Organic Light‐emitting Dementioning

confidence: 99%

Recent Developments in Flexible Organic Light‐Emitting Devices

Liu

Feng

et al. 2018

Adv Materials Technologies

Self Cite

117

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“…Even though theory predicts that light harvesting by periodic structures can be better than that of random structures, devices with random structures still show enhanced performance and are less wavelength sensitive. Randomly distributed scattering layers of NPs have been implemented into OLEDs and OPV because of their superior merits in terms of cost and easy processing. In previous studies, the scattering layers were often made by mixing NPs, with a high refractive index, into a transparent polymer matrix such as propylene glycol‐monomethyl‐ether acetate (PGMEA) or polystyrene (PS) .…”

Section: Optical In‐couplingmentioning

confidence: 99%

Optical In‐Coupling in Organic Solar Cells

2018

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thus offering an environmentally friendly approach. Furthermore, the use of simple low-temperature processing techniques makes it a potentially low-cost technology. However, efficiency and stability are so far lacking, hampering the full exploitation of the potential this technology has in these new applications. After the demonstration of the first reasonably performing organic solar cell by Tang [1] achieving approximately 1% efficiency, much effort has been put into improving these values. Nowadays, efficiencies well beyond 10%, and even over 13% have been reached, [2,3] however, with hard-to-synthesize polymers that so far have not shown sufficient stability for practical applications.Closer to commercial exploitation, solar cells based on oligomers (also termed "small molecules") and the material class used by Tang et al. [1] are investigated and introduced in their pioneering papers. [4][5][6][7][8][9][10][11][12][13][14][15] This material class can be either deposited by vacuum evaporation or solution processing. [16][17][18][19][20][21] The advantage of vacuum evaporation is that very pure layers without solvent residuals are produced, which is favorable for a higher stability of the cells. Also, they allow several cells to be very easily integrated into stacked multijunction devices. [22] With multijunction cells, Heliatek has reached an efficiency of 13.2% using proprietary materials that allow long lifetimes and can be readily manufactured. [23] Single-junction devices with similar published materials achieve above 8% efficiency [24] and above 10% in single-junction and tandem devices, respectively. [25] While these values are much improved as compared to the pioneering work of Tang, there is still a large gap to be closed to reach efficiencies comparable to silicon solar cells and other inorganic PV technologies.Here, first we will address limitations of organic solar cells, such as short exciton diffusion length, voltage, and transport problems. After that, various approaches to solve these challenges will be introduced. These include the bulk heterojunction, multijunction devices, and periodically patterned structures on substrates or active layers. Among these approaches, we focus on optical in-coupling, which allows more photons to be funneled into the thin organic active layers, yielding higher efficiencies. Limitations of Organic Solar CellsAlthough organic solar cells have huge potential and acceptable power conversion efficiencies (PCEs), they still have limitations caused by a short exciton diffusion length, charge transport, and low open-circuit voltage (V oc ). In this section, we briefly summarize why OSCs lack in efficiency, and optical in-coupling is required to improve the performance.Organic photovoltaics have many unique properties, such as flexibility, transparency, and low weight, which allows novel applications to be addressed. A remaining challenge is to increase the power conversion efficiencies into the range that is offered by conventional inorganic photovoltaics. Due to the li...

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“…12 The periodic or random microstructure substrate usually involve multi steps, which is difficult to make. 13 Here in our work, we nd a simple new method for the preparation of nanostructures. The deposited tris(8-quinolinolato)aluminum (Alq 3 ) lm is placed under the uncured UV adhesive atmosphere for 12 hours, the Alq 3 lm gets corrugated.…”

Section: Introductionmentioning

confidence: 99%

Enhanced outcoupling efficiency and removal of the microcavity effect in top-emitting OLED by using a simple vapor treated corrugated film

Huang

et al. 2017

RSC Adv.

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We proposed a simple new method to form organic corrugated film. 50 nm tris(8-quinolinolato)aluminum film which was deposited on a glass substrate was put into an uncured ultraviolet (UV) adhesive atmosphere with active ingredient acrylate monomer. After 12 hours of treatment a corrugated film with nano grains was formed, the surface roughness was changed from 1.8 nm to 26 nm, which was caused by solvent-induced crystallization under the uncured UV adhesive atmosphere. We studied the film morphology, UV absorption and photoluminescence. The optical haze effect was also measured. By using the corrugated film in top emitting organic light-emitting diodes, the microcavity effect was eliminated, and the out-coupling efficiency was obviously improved, and the efficiency improvement was a result of the scattering of the surface plasma mode.

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Light manipulation in organic light‐emitting devices by integrating micro/nano patterns

Cited by 57 publications

References 210 publications

Recent Developments in Flexible Organic Light‐Emitting Devices

Recent Developments in Flexible Organic Light‐Emitting Devices

Optical In‐Coupling in Organic Solar Cells

Enhanced outcoupling efficiency and removal of the microcavity effect in top-emitting OLED by using a simple vapor treated corrugated film

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