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Organic light emitting diodes (OLED) are expected to be used in next generation solid state lighting sources serving as an alternative to conventional incandescent bulbs and fluorescent lamps. OLEDs will provide the environmental benefits of possible considerable energy savings and elimination of mercury, as well as some other advantages such as th...
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... the field of lighting, environmental issues are also very important. Figure 1 shows the total electric power consumption worldwide in 2005 1 . About 19 % of the total energy was consumed in lighting and was equivalent to a huge amount of 1,900 mega tons of CO 2 emission. ...
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... structure of a typical two-unit OLED is shown in figure 10. A blue fluorescent unit, a transparent connecting layer, a green and red phosphorescent unit, and an aluminum cathode were deposited onto a transparent substrate with some patterned electrodes. ...
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... the optical design of the device structure is done with the goals of optimizing both internal and external optical behaviors. Figure 11 shows the examples of the angular dependence of CIE coordinates of (A) optically designed two-unit OLED and (B) non-designed two-unit OLED, respectively. The large angular dependence shown in device B is significantly reduced in device A with better optical design. of (A) optically designed OLED and (B) non-designed OLED ...
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... emission spectrum of device A at 1,000 cd/m 2 , current density -voltage and the luminous efficiency - luminance characteristics are shown in figure 12 and figure 13, respectively. A high CRI of 88 at CIE chromaticity coordinates of (0.38, 0.40) and high luminous efficiency of 37 lm/W at 100 cd/m 2 and 28 lm/W at 1,000 cd/m 2 are obtained. ...
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Citations
... The emitted color and the intensity of the colors and brightness is dependent on the electric current supplied. They are versatile, self-emitting, temperature resistant, and require thinner layers than conventional lighting technologies [125][126][127]. ...
Due to the demand for materials that have promising properties for the electronic device market, the development of new conjugated polymers, where the π bond is responsible for the material's optoelectronic properties, has attracted the attention of the academic and industrial community owing to the easy processability, which can be performed from a polymeric solution, and to a great potential for the manufacture of devices such as cell phone screens, televisions, light-emitting diodes, and solid-state lighting (SSL). For SSL applications, usually, polymers capable of emitting red, green, and blue (RGB) light bands are used, which combined, generate white light. Thus, this review presents some of the most relevant works that aim at developing RGB devices that can be used for SSL applications.
... In today's state-of-the-art of semiconductor technologies, organic semiconductors have both demonstrated their ability to achieve technological applications at the consumer-electronic market-level [1,2], and continues to inspire the scientific community by unlocking truly disruptive abilities to realize next-generation electronics [3][4][5]. For their potentials for lowcost electronics [6], soft processing, and device added features such as flexibility or transparency [7], these materials have been widely investigated in a range of microelectronic and optoelectronic architectures such as field-effect transistors [8], light-emitting PN-diodes (OLEDs) [9], Schottky diodes [10] and single carrier sensing devices [11]. ...
Simultaneously optimizing performances, processability and fabrication cost of organic electronic materials is the continual source of compromise hindering the development of disruptive applications. In this work, we identified a strategy to achieve record conductivity values of one of the most benchmarked semiconducting polymers by doping with an entirely solution-processed, water-free and cost-effective technique. High electrical conductivity for poly(3-hexylthiophene) up to 21 S/cm has been achieved, using a commercially available electron acceptor as both a Lewis acid and an oxidizing agent. While we managed water-free solution-processing a three-time higher conductivity for P3HT with a very affordable/available chemical, near-field microscopy reveals the existence of concentration-dependent higher-conductivity micro-domains for which furthermore process optimization might access to even higher performances. In the perpetual quest of reaching higher performances for organic electronics, this work shall greatly unlock applications maturation requiring higher-scale processability and lower fabrication costs concomitant of higher performances and new functionalities, in the current context where understanding the doping mechanism of such class of materials remains of the greatest interest.
... In today's state-of-the-art of semiconductor technologies, organic semiconductors have both demonstrated their ability to achieve technological applications at the consumer-electronic market-level [1,2], and continues to inspire the scientific community by unlocking truly disruptive abilities to realize next-generation electronics [3][4][5]. For their potentials for lowcost electronics [6], soft processing, and device added features such as flexibility or transparency [7], these materials have been widely investigated in a range of microelectronic and optoelectronic architectures such as field-effect transistors [8], light-emitting PN-diodes (OLEDs) [9], Schottky diodes [10] and single carrier sensing devices [11]. ...
Simultaneously optimizing performances, processability and fabrication cost of organic electronic materials is the continual source of compromise hindering the development of disruptive applications. In this work, we identified a strategy to achieve record conductivity values of one of the most benchmarked semiconducting polymers by doping with an entirely solution-processed, water-free and cost-effective technique. High electrical conductivity for poly(3-hexylthiophene) up to 21 S/cm has been achieved, using a commercially available electron acceptor as both a Lewis acid and an oxidizing agent. While we managed water-free solution-processing a three-time higher conductivity for P3HT with a very affordable/available chemical, near-field microscopy reveals the existence of concentration-dependent higher-conductivity micro-domains for which furthermore process optimization might access to even higher performances. In the perpetual quest of reaching higher performances for organic electronics, this work shall greatly unlock applications maturation requiring higher-scale processability and lower fabrication costs concomitant of higher performances and new functionalities, in the current context where understanding the doping mechanism of such class of materials remains of the greatest interest.
... The vision of solid state lighting has largely been driven firstly by the desire to reduce energy consumption and secondly to get pollution free light generation. Today, OLEDs are promising for their applications as solid state lighting devices [169][170][171][172][173][174][175][176][177][178][179][180][181]. The incandescent light bulbs and fluorescent tubes have several drawbacks; therefore, in recent years the researchers are making great efforts to replace them by solid state lighting (SSL) devices. ...
Organic light emitting diodes (OLEDs) have been the focus of intense study since the late 1980s, when the low voltage organic electroluminescence in small organic molecules such as Alq3, and large organic molecules such as polymers (PPV), was reported. Since that time, research has continued to demonstrate the potential of OLEDs as viable systems for displays and eco-friendly lighting applications. OLEDs offer full colour display, reduced manufacturing cost, larger viewing angle, more flexible, lower power consumption, better contrast, slimmer, etc. which help in replacing the other technologies such as LCD. The operation of OLEDs involves injection of charge carriers into organic semiconducting layers, recombination of charge carriers, formation of singlet and triplet excitons, and emission of light during decay of excitons. The maximum internal quantum efficiency of fluorescent OLEDs consisting of the emissive layer of fluorescent organic material is 25% because in this case only the 25% singlet excitons can emit light. The maximum internal quantum efficiency of phosphorescent OLEDs consisting of the emissive layer of fluorescent organic material mixed with phosphorescent material of heavy metal complexes such as platinum complexes, iridium complexes, etc. is nearly 100% because in this case both the 25% singlet excitons and 75% triplet excitons emit light. Recently, a new class of OLEDs based on thermally activated delayed fluorescence (TADF) has been reported, in which the energy gap between the singlet and triplet excited states is minimized by design, thereby promoting highly efficient spin up-conversion from non-radiative triplet states to radiative singlet states while maintaining high radiative decay rates of more than 106 decays per second. These molecules harness both singlet and triplet excitons for light emission through fluorescence decay channels and provides an intrinsic fluorescence efficiency in excess of 90 per cent and a very high external electroluminescence efficiency of more than 19 per cent, which is comparable to that achieved in high-efficiency phosphorescence-based OLEDs.The OLED technology can be used to make screens large enough for laptop, cell phones, desktop computers, televisions, etc. OLED materials could someday be applied to plastic and other materials to create wall-size video panels, roll-up screens for laptops, automotive displays, and even head wearable displays. Presently, the OLEDs are opening up completely new design possibilities for lighting in the world of tomorrow whereby the offices and living rooms could be illuminated by lighting panels on the ceiling. The present paper describes the salient features of OLEDs and discusses the applications of OLEDs in displays and solid state lighting devices. Finally, the challenges in the field of OLEDs are explored.
Contents of Paper
... Organic light-emitting diodes (OLEDs) will provide a new generation of lighting sources. 1,2 This solid state light source is a "green-energy" source with low power consumption and high energy savings without using mercury. It is a low-cost technology that enables many nice applications, such as flexible and shaped panel, large-area sources, and diffuse and planar emission. ...
Large-area top-emitting PIN structure (highly p-and n-type doped transport layers for electrons and holes and an undoped emitter layer)–organic light-emitting diode (OLED) on advanced metal foils were fabricated for lighting applications. ArcelorMittal has developed a new surface treatment on metal foils, suitable for roll-to-roll production and dedicated to large-area device integration. Both monochromatic and white devices are realized on advanced metal foils. Power efficiencies at 1000 cd/m 2 of >70 lm/W (green), moreover, power efficiency of white devices of >22 lm/W are achieved. Furthermore, first large-area 60 × 60 cm white OLED sources on metal foils are presented. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).
... In the recent years progress has been made to develop large light panels on transparent ITO (indium tin oxide) coated glass substrates (e.g. [1], [2] and [4]). However the price for ITO has been increased over the last years significant. ...
OLED technology has successfully penetrated the display market within the last years. To enable OLED technology for further markets like signage and general lighting, cost reduction is a major issue. The use of ITO coated glass substrates as used for passive matrix displays is therefore not an option for lighting application. Low cost metal foil as substrate for the deposition of organic light-emitting diodes will allow a major cost reducing step. Furthermore there is a need to replace sheet to sheet fabrication technologies by roll-to-roll-processing. Within the "Center of Organic Materials and Electronic Devices Dresden" (COMEDD) of Fraunhofer IPMS a roll-to-roll line for research and development in OLED lighting is currently under installation
Herein, two new solution‐processable HLCT fluorophores (CBzF and CBzFC) based on benzothiadiazole (Bz) derivatives were designed and synthesized (HLCT=hybridized local and charge transfer). Their optical and photophysical properties were experimentally and theoretically studied and verified by the solvatochromic effect and density functional theory calculations. The two molecules demonstrate high solubility, HLCT features, and an intense green fluorescence with solid‐state photoluminescence quantum yields of 63–72 %. Both fluorophores are effectively applied as non‐doped emitters for solution‐processed double‐layered OLEDs, which produce intense green emission colors with low turn‐on voltages (3.0–3.2 V). Specifically, the CBzFC‐based solution‐processed device achieves a high maximum luminescence (24400 cd m⁻²), high maximum efficiencies (EQEmax=5.59 %, CEmax=12.24 cd A⁻¹, and PEmax=10.54 lm W⁻¹), and decent efficiency low‐off.
The ortho-substituted donor-acceptor molecules 2-(4,6-diphenyl-1, 3, 5-triazin-2-yl)-N,Ndiphenylaniline (DPA-o-Trz) and 2-(4,6-diphenyl-1, 3, 5-triazine-2-yl)-N,N-di-p-tolylaniline (MPA-o-Trz) were designed, synthesized, and found to exhibit green fluorescence characteristics. Notably, the singlet-triplet energy gap was less than 0.1 eV, indicating that reverse intersystem crossing gave rise to thermally activated delayed fluorescence (TADF). The organic light-emitting device performance of MPA-o-Trz showed a high external quantum efficiency of 16.3% and good color stability from 0.1 cd/m² to 5000 cd/m².
We investigated some effective device designs and fabrication methods for long operation-lifetime all-solution-processed Phosphorescent OLEDs (PhOLEDs) and fluorescent OLEDs with mixed-hosts system and thin Poly [(9, 9-dioctylfluorenyl-2, 7-diyl)-co-(4, 4′-(N-(4-sec-butylphenyl) diphenylamine)] (TFB). The all-solution-processed green PhOLEDs had high current efficiency (30.3 cd/A) and long operation-lifetime. The best half-lifetime of green PhOLEDs with thin HTL, MH-hosts EML and optimized deposition was 310 h at an initial luminance 1000 cd/m², 250 h at an initial luminance 500 cd/m² for green PhOLEDs with thin HTL, and MH-hosts EML, and the lifetime of triple layer PhOLEDs device was only 0.5 h for the same materials. The red PhOLEDs exhibited a high current efficiency (10.93 cd/A) and half-lifetime with 157.9 h at an initial luminance 500 cd/m². For the blue fluorescent OLEDs, the thin polymer TFB, mixed-hosts EML, double EMLs and optimization deposition yield a high current efficiency (5.68 cd/A) and long operation-lifetime with 117.7 h at an initial luminance 500 cd/m². Single host fluorescent device had half-lifetime of 73.5 h only at an initial luminance 100 cd/m². Finally, by doping red emitter Rubrene into stable blue device, we achieved soft yellow OLEDs with high efficiency (10.87 cd/A) and 8 fold improvement operation-lifetime (1200 h). We believe that such all-solution-processed OLEDs which showed greatly improved operational lifetimes would be suitable for the indoor supportive lighting with natural colors.
A high performance multi-unit OLED device having excellent emission characteristics of luminous efficacy of 37 Im/W and color rendering index of 95 and very small variation of chromaticity in different directions is developed. Stable emission at high luminance in a large OLED panel and long storage stability are realized with a heat radiative thin encapsulation.
