Browsing by Author "Wong, Ken-Tsung"

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A demonstration of solid-state white light-emitting electrochemical cells using the integrated on-chip plasmonic notch filters
(2016)
Lee, Ya-Ju
;
Lin, Chia-Ching
;
Lee, Hsiao-Chin
;
Yao, Yung-Chi
;
Sarma, Monima
In this study, we demonstrate solid-state white light-emitting electrochemical cells (LECs) using an integrated plasmonic notch filter to tailor the electroluminescence (EL) spectrum of non-doped blue-green emissive material. The plasmonic notch filter is composed of randomly distributed silver nanoparticles (Ag-NPs) embedded in the anode contact of indium tin oxide (ITO). This plasmonic notch filter strongly absorbs green light due to local surface plasmon (LSP) resonance of the Ag-NPs embedded in ITO. Thus, the emission green light of the solid-state LEC is strongly suppressed, leaving the blue and red light output to generate a white EL emission. Moreover, the duration of white EL can be maintained for a longer time under operation, which overcomes the issues regarding the short lifetime of white EL generated by the microcavity effect. In addition, the Ag-NPs can be readily fabricated by the thermal annealing of Ag film, which is compatible with current fabrication technologies typically used in light-emitting diode (LED) industry. Therefore, solid-state white LECs using an integrated on-chip plasmonic notch filter have great potential for applications in solid-state lighting.
Adjusting Color Temperature of Electroluminescence from White Light-Emitting Electrochemical Cells by Laser-Scanned Annealing of Nanoparticles
(2017-01-01)
Lee, Hsiao-Chin
;
Chiang, Chien-Ming Fan
;
Wu, Po-Yi
;
Yao, Yung-Chi
;
Sarma, Monima
Color temperature of electroluminescence from white light-emitting electrochemical cells can be adjusted by locally laser-scanned thermal annealing on a semi-continuous thin Ag film embedded between indium tin oxide anode and glass substrate. The proposed technique offers programmable versatility to control white electroluminescence and is compatible with display manufacturing technologies.
An ionic terfluorene derivative for saturated deep-blue solid state light-emitting electrochemical cells
(2011)
Chen, Hsiao-Fan
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Liao, Chih-Teng
;
Chen, Te-Chuan
;
Su, Hai-Ching
;
Wong, Ken-Tsung
In this study, we obtained saturated deep-blue electroluminescence (EL) from solid state light-emitting electrochemical cells (LECs) incorporating the ionic terfluorene derivative 1, which we synthesized through covalent tethering of methylimidazolium moieties as pendent groups of terfluorene. Compound 1 exhibited the deep-blue emission, extremely high quantum yield, and reversible redox behavior that are characteristic of terfluorene derivatives. LEC devices incorporating terfluorene 1 exhibited deep-blue EL with CIE coordinates of (0.159, 0.115) and (0.151, 0.122) in the absence and presence, respectively, of the ionic liquid (IL) BMIM center dot PF(6). The peak external quantum efficiency and peak power efficiency of 1 in the presence of the IL reached 1.14% and 1.24 lmW(-1), respectively. These CIE coordinates are the most saturated blue emissions ever reported for LECs.
Bis(diphenylamino)-9,9 '-spirobifluorene functionalized Ir(III) complex: a conceptual design en route to a three-in-one system possessing emitting core and electron and hole transport peripherals
(2011)
Chen, Hsiao-Fan
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Wong, Ken-Tsung
;
Liu, Yi-Hung
;
Wang, Yu
;
Cheng, Yi-Ming
Conceptual design of a three-in-one (luminescence chromophore with electron and hole transports) system was demonstrated by a functionalized Ir(III) complex 3, in which 4,5-diazafluorene and bis(diphenylamino) serve as electron and hole transporting sites, respectively. The poor emission quantum yield of 3 was systematically examined via a series of photophysical studies in combination with theoretical approaches. The far lifting of the pi-electron from -NPh(2) renders virtually no (3)MLCT contribution to the lowest transition in the triplet manifold as compared with that of the parent model 2 without amino substituents. With an empirical approach, we conclude that an energy gap law may account for the major deactivation process. A light-emitting electrochemical cell (LEC) device based on 3 shows peak EQE, peak current efficiency and peak power efficiency at 2.4 V of 0.020%, 0.013 cd A(-1) and 0.017 lm/W, respectively. The low device efficiencies are in accordance with the low PL quantum yield, stemming from the ligand-centered radiationless deactivation. The conceptual design presented here should provide valuable information for future progress en route to an ideal three-in-one system suited for OLEDs.
Blade coating of Tris(8-hydroxyquinolinato)aluminum as the electron-transport layer for all-solution blue fluorescent organic light-emitting diodes
(2016-02-01)
Chang, Yu-Fan
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Meng, Hsin-Fei
;
Fan, Gang-Lun
;
Wong, Ken-Tsung
;
Zan, Hsiao-Wen
Organic light-emitting diodes (OLEDs) with a low driving voltage and efficient blue fluorescence were fabricated through blade coating. Tris(8-hydroxyquinolinato)aluminum (Alq(3)) is a relatively stable electron-transporting material commonly used in evaporation. However, depositing Alq(3) through a solution process is difficult because of its extremely low solubility organic solvents, a result of its symmetrical molecular structure. In this study, Alq(3) was successfully deposited through blade coating at a very low concentration below 0.1wt%. The OLEDs contained co-dopants BUBD-1 and p-bis(p-N,N-diphenyl-aminostyryl)benzene (DSA-Ph), and a high-band-gap host 2-methyl-9,10-bis(naphthalen-2-yl) anthracene (MADN) as the emission layer with the following structure: ITO/PEDOT:PSS (40 nm)/VB-FNPD (30 nm)/MADN:2% BUBD-1:1% DSA-Ph (50 nm)/TPBI (30 nm)/LiF (0.8 nm)/Al (100 nm)or ITO/PEDOT:PSS (40 nm)/VB-FNPD (30 nm)/MADN:3% BUBD-1 (50 nm)tris(8-hydroxyquinolinato)aluminum (Alq(3); 10 nm)/LiF (0.8 nm)/Al (100 nm). 2,7-disubstituted fluorene-based triaryldiamine(VB-FNPD)is the cross-linking transporting material. The device exhibited a peak current efficiency of 5.67 cd/A for Alq(3) and 5.76 cd/A for TPBI. The device with Alq(3) has operated lifetime seven times higher than the device with TPBI. (C) 2015 Elsevier B.V. All rights reserved.
Cationic Iridium Complexes with Intramolecular pi-pi Interaction and Enhanced Steric Hindrance for Solid-State Light-Emitting Electrochemical Cells
(2012-11-19)
Chen, Hsiao-Fan
;
Hung, Wen-Yi
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Chen, Shou-Wei
;
Wang, Ting-Chih
;
Lin, Shih-Wei
Cationic iridium complexes incorporated 4,5-diaza-9,9'-spirobifluorene as N<^>N ancillary ligands, in which one (2) or two (3) phenyl groups were introduced onto 4,5-diazafluorene to afford intraligand pi-pi interactions. The X-ray crystal structures of complexes 2 and 3 show that the pendant phenyl ring forms strong intramolecular face-to-face pi-stacking with the difluorophenyl ring of the cyclometalated ligand with distances of 3.38 angstrom for complex 2 and 3.40 and 3.46 angstrom for complex 3. This pi-pi stacking interaction minimizes the expansion of the metal ligand bonds in the excited state, resulting in a longer device lifetime in the light-emitting electrochemical cell (LEC) devices.
Cofacial Versus Coplanar Arrangement in Centrosymmetric Packing Dimers of Dipolar Small Molecules: Structural Effects on the Crystallization Behaviors and Optoelectronic Characteristics
(2016-07-20)
Chou, Shu-Hua
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Kang, Hao-Wei
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Chang, Shu-Ting
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Wu, Kuan-Yi
;
Bazan, Guillermo C.
Two D-pi-A-A molecules (MIDTP and TIDTP) composed of an electron-rich ditolylamino group (D) and an electron-deficient 5-dicyanovinylenylpyrimidine (A-A) fragment bridged together with indeno[1,2-b]thiophene (IDT) were synthesized. These molecules provide an opportunity to examine in-depth the impact of side-chain variations (methyl vs p-tolyl) on the crystallization behaviors, solid-state morphology, physical properties, and optoelectronic characteristics relevant for practical applications. X-ray analyses on single-crystal structures indicate that methyl-substituted MIDTP forms coplanar antiparallel dimers via C-H center dot center dot center dot S interactions and organizes into an ordered slip-staircase arrays. In contrast, p-tolyl-bearing TIDTP shows cofacial centrosymmetric dimers via pi-pi interactions and packs into a less-ordered layered structures. The X-ray diffraction analyses upon thermal treatment are consistent with a superior crystallinity of MIDTP, as compared to that of TIDTP. This difference indicates a greater propensity to organization by introduction of the smaller methyl group versus the bulkier p-tolyl group. The increased propensity for order by MIDTP facilitates the crystallization of MIDTP in both solution-processed and vacuum-deposited thin films. MIDTP forms solution-processed single-crystal arrays that deliver OFET hole mobility of 6.56 x 10(-4) cm(2) V-1 s(-1), whereas TIDTP only forms amorhpous films that gave lower hole mobility of 1.34 x 10(-5) cm(2) V-1 s(-1). MIDTP and TIDTP were utilized to serve as donors together with C-70 as acceptor in the fabrication of small-molecule organic solar cells (SMOSCs) with planar heterojunction (PHJ) or planar-mixed heterojunction (PMHJ) device architectures. OPV devices based on higher crystalline MIDTP delivered power conversion efficiencies (PCEs) of 2.5% and 4.3% for PHJ and PMHJ device, respectively, which are higher than those of TIDTP-based cells. The improved PCEs of MIDTP-based devices are attributed to better hole-transport character.
Dynamically tuning the correlated color temperature of white light-emitting electrochemical cells with electrochromic filters
(2017-09-01)
Chiou, Bo-Ruei
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Lee, Hsiao-Chin
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Jang, Yea-Fen
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Yang, Zu-Po
;
Wang, Yao-Chin
Recently, white solid-state light-emitting electrochemical cells (LECs) have drawn great attention since they exhibit advantages such as low-voltage operation, compatibility with solution processes and employing inert cathode metals. Since different correlated color temperatures (CCTs) of background illumination are necessary for various lighting applications, a real-time tunable CCT of white LECs would be highly desired in modern smart lighting systems. In this work, a widely and dynamically tuning CCT (>10000 K) of white LEC is demonstrated by employing an electrochromic device (ECD) as a real-time controllable color filter. By increasing the applied bias on the ECD to attenuate more the red parts of white EL from the white LEC, the LEC-based white light source becomes more bluish and, in consequence, shows higher CCT. This proposed LEC-based white light source with the characteristics of wide CCT range and real-time tunability is suitable for most lighting applications and modern smart lighting systems. (C) 2017 Elsevier B.V. All rights reserved.
Efficient and color-stable solid-state white light-emitting electrochemical cells employing red color conversion layers
(2012-03-01)
Wu, Hung-Bao
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Chen, Hsiao-Fan
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Liao, Chih-Teng
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Su, Hai-Ching
;
Wong, Ken-Tsung
We report efficient and color-stable white light-emitting electrochemical cells (LECs) by combining single-layered blue-emitting LECs with red-emitting color conversion layers (CCLs) on the inverse side of the glass substrate. By judicious choosing of the red-emitting dye doped in CCLs, good spectral overlap between the absorption spectrum of the red-emitting dye and the emission spectrum of the blue-emitting emissive material results in efficient energy transfer and thus sufficient down-converted red emission at low doping concentrations of the red-emitting dye in the CCLs. Low doping concentration is beneficial in reducing self-quenching of the red-emitting dye, rendering efficient red emission. Electroluminescent (EL) measurements show that the peak external quantum efficiency and the peak power efficiency of the white LECs employing red CCLs reach 5.93% and 15.34 lmW (1), respectively, which are among the highest reported for white LECs. Furthermore, these devices exhibit bias-insensitive white EL spectra, which are required for practical applications, due to nondoped emissive layers. These results reveal that single-layered blue-emitting LECs combined with red-emitting CCLs are one of the potential candidates for efficient and color-stable white light-emitting devices. (C) 2011 Elsevier B. V. All rights reserved.
Efficient solid-state white light-emitting electrochemical cells based on phosphorescent sensitization
(2012-11-21)
Su, Hai-Ching
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Chen, Hsiao-Fan
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Chen, Po-Hsien
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Lin, Shih-Wei
;
Liao, Chih-Teng
Efficient phosphorescent sensitized white light-emitting electrochemical cells (LECs) based on a blue-emitting phosphorescent cationic transition metal complex (CTMC) doped with a red-emitting fluorescent dye are demonstrated. Blue phosphorescence and phosphorescence-sensitized red fluorescence contribute to white emission. Furthermore, the microcavity effect of the device structure is utilized to suppress the green part of the electroluminescence (EL) spectrum of the blue-emitting phosphorescent metal complex (1) via destructive interference. Hence, more saturated blue EL emission can be obtained. When combined with saturated red emission, white EL emission with Commission Internationale de l'Eclairage coordinates approaching (0.33, 0.33) can be obtained without the need for saturated deep-blue emitting CTMCs. Peak external quantum efficiency and power efficiency of the phosphorescence sensitized white LECs are up to 7.9% and 15.6 lm W-1, respectively. These efficiencies are among the highest reported for white LECs and reveal that phosphorescent sensitization is useful for improving device efficiencies of white LECs.
Efficient solid-state white light-emitting electrochemical cells employing embedded red color conversion layers
(2015-01-01)
Lu, Jung-Sheng
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Chen, Hsiao-Fan
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Kuo, Jung-Chin
;
Sun, Ray
;
Cheng, Chia-Yu
Recently, white light-emitting electrochemical cells (LECs) have attracted scientific attention due to their advantages of simple device structure, low operation voltage and compatibility with solution processes. In this work, efficient white emission from blue-emitting LECs with embedded red color conversion layers (CCLs) is reported. The red CCL is embedded between an indium tin oxide (ITO) layer and a glass substrate. The blue electroluminescence (EL) trapped in the waveguided mode, i.e. in the ITO layer, shows an evanescent tail in the CCL layer and excites the red-emitting dye, generating red photoluminescence (PL). Because the trapped blue EL can be partially transferred to the out-coupled red PL, the doping concentration of the red dye in the CCL can be reduced, and thus the absorption loss of the blue EL in the forward direction (air mode) can be mitigated, rendering enhanced device efficiency. The peak external quantum efficiency and power efficiency obtained in the blue-emitting LECs with embedded red CCLs are up to 12.5% and 27 lm W-1, respectively. These values are among the highest reported for white LECs, and thus confirm that blue-emitting LECs containing embedded red CCLs are capable of providing efficient white emission.
Enhancing device efficiencies of solid-state white light-emitting electrochemical cells by employing waveguide coupling
(2015-01-01)
Cheng, Chia-Yu
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Wang, Chi-Wei
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Cheng, Jing-Rong
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Chen, Hsiao-Fan
;
Yeh, Yun-Shiuan
Solid-state white light-emitting electrochemical cells (LECs) have received intense scientific attention owing to their potential applications in display and lighting. Although device efficiencies of white LECs have been significantly improved in recent years, further improvements are still required for their practical applications. In this work, we demonstrate the enhancement of device efficiencies of white LECs by employing waveguide coupling. Two transparent photoresist (TPR) layers doped with TiO2 nanoparticles (NPs) are inserted between the indium tin oxide (ITO) layer and the glass substrate. By tuning the doping concentration of 25 nm TiO2 NPs in the upper TPR layer to adjust the refractive index, effective waveguide coupling between the ITO layer and the lower TPR layer can be achieved. Since the lower TPR layer contains 250 nm TiO2 NPs, electroluminescence (EL) outcoupled from the ITO layer can be scattered and redirected into the forward direction. Furthermore, the EL trapped in the glass substrate can also transmit into the lower TPR layer and then is scattered to the forward direction. When the EL trapped in the ITO layer and the glass substrate can be effectively recycled into the forward direction, the peak external quantum efficiency and power efficiency obtained in white LECs employing waveguide coupling are up to 19.4% and 34.1 lm W-1, respectively. These efficiencies are among the highest reported for white LECs and thus confirm that waveguide coupling would be useful for realizing highly efficient white LECs. In addition to the enhanced device efficiencies, improved color migration of EL spectra, which is desired for lighting applications, can be obtained in white LECs with scattering waveguide layers since EL of different angles can be mixed in the forward direction.
Highly efficient double-doped solid-state white light-emitting electrochemical cells
(2011)
Su, Hai-Ching
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Chen, Hsiao-Fan
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Shen, Yu-Chun
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Liao, Chih-Teng
;
Wong, Ken-Tsung
We report highly efficient, solid-state, white light-emitting electrochemical cells (LECs) based on a double-doped strategy, which judiciously introduces an orange-emitting guest, [Ir(ppy)(2)(dasb)](+)(PF(6)(-)), into a single-doped emissive layer comprised of an efficient blue-green emitting host, [Ir(dfppz)(2)(dtb-bpy)](+)(PF(6)(-)), and a red-emitting guest, [Ir(ppy)(2)(biq)](+)(PF(6)(-)), to improve the balance of carrier mobilities and, thus, to enhance the device efficiency. Photoluminescence (PL) measurements show that the single-doped (red guest) and the double-doped (red and orange guests) host-guest films exhibit similar white PL spectra and comparable photoluminescence quantum yields, while the device efficiencies of the double-doped white LECs are twofold higher than those of the single-doped white LECs. Therefore, such enhancement of the device efficiency is rationally attributed to the improved balance of carrier mobilities of the double-doped emissive layer. Peak external quantum efficiency and peak power efficiency of the double-doped white LECs reached 7.4% and 15 lm W(-1), respectively. These efficiencies are amongst the highest reported for solid-state white LECs and, thus, confirm that the double-doping strategy is useful for achieving highly efficient white LECs.
Highly efficient exciplex emission in solid-state light-emitting electrochemical cells based on mixed ionic hole-transport triarylamine and ionic electron-transport 1,3,5-triazine derivatives
(2013)
Chen, Hsiao-Fan
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Liao, Chih-Teng
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Su, Hai-Ching
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Yeh, Yun-Shiuan
;
Wong, Ken-Tsung
Highly efficient exciplex emission in solid-state light-emitting electrochemical cells (LECs) was achieved by mixing two ionic fluorescent emitters with opposite bipolarity. A triarylamine derivative as a hole-transport material (HTM) and a 1,3,5-triazine derivative as an electron-transport material (ETM) were selected due to their superior carrier mobilities. The ionic character of HTM and ETM was achieved by chemically attaching three pendant methylimidazolium groups as peripheries, rendering them amenable to LEC applications. Strong exciplex green emission can be observed either from photoluminescence in solid states or electroluminescence in LEC devices when HTM and ETM are mixed. By optimizing the mixing ratio, the external quantum efficiency and power efficiency can be achieved up to 3.04% and 10.29 lm W-1, respectively. These results are among the highest reported for fluorescent LECs.
Highly efficient organic solar cells using a solution-processed active layer with a small molecule donor and pristine fullerene
(2014)
Lin, Hao-Wu
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Chang, Jung-Hao
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Huang, Wei-Ching
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Lin, Yu-Ting
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Lin, Li-Yen
A new strategy has been successfully established to realize high efficiency small molecule organic solar cells with a solution-processed active layer composed of a small organic molecule as the donor and pristine C-70 as the acceptor. Using 1,2-dichlorobenzene as solvent, a homogeneous donor/C-70 blend active layer can be effectively formed either by spin- or bar-coating techniques. This method delivers organic solar cells with high power conversion efficiencies up to 5.9%.
Improving color saturation of blue light-emitting electrochemical cells by plasmonic filters
(2017-12-01)
Chiang, Chien-Ming Fan
;
Chang, Bo-Ren
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Lee, Ya-Ju
;
Sarma, Monima
;
Yang, Zu-Po
In consideration of the advantages of light-emitting electrochemical cells (LECs), it is desired to develop the saturated blue LECs for LEC display, which is hindered by the features of broad emission spectrum and emission peak not short enough. In this study, we demonstrated a novel method to improve blue saturation of the sky-blue LECs by engineering its emission spectrum through the plasmonic filters. These plasmonic filters composed of randomly distributed silver nanoparticles (Ag-NPs) can absorb the green and red emission tail of the sky-blue LECs due to localized surface plasmon resonance (LSPR). The LSPR wavelengths of Ag-NPs are tuned by manipulating the effective refractive index of materials around Ag-NPs through the accurate control of the TiO2 thickness using atomic layer deposition technique. By integrating with the plasmonic filters, the CIE1931 coordinate of the blue LECs can approach to (0.14, 0.22), which is comparable to or even better than the reported bluest values of blue LECs. Combination with the green and red LECs, the color gamut increases from 34% (without filters) to 54% of National Television System Committee (NTSC) color gamut, corresponding to 1.6 times enhancement. In addition, the blue LECs integrated with plasmonic filters still have better efficiency than those of the reported bluest LECs. (C) 2017 Elsevier B.V. All rights reserved.
Improving device efficiencies of solid-state white light-emitting electrochemical cells by adjusting the emissive-layer thickness
(2013-10-01)
Jhang, Yuan-Pei
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Chen, Hsiao-Fan
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Wu, Hung-Bao
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Yeh, Yun-Shiuan
;
Su, Hai-Ching
Exciton quenching in the recombination zone close to electrochemically doped regions would be one of the bottlenecks for improving device efficiencies of solid-state white light-emitting electrochemical cells (LECs). To further enhance device efficiencies of white LECs for practical applications, we adjust the emissive-layer thickness to reduce exciton quenching. In white LECs with properly thickened emissive-layer thickness, the recombination zone can be situated near the center of the emissive layer, rendering mitigated exciton quenching and thus enhanced device efficiencies. High external quantum efficiencies and power efficiencies of optimized devices reach ca. 11% and 20 lm/W, respectively, which are among the highest reported for white LECs. These results confirm that tailoring the thickness of the emissive layer to avoid exciton quenching would be a feasible approach to improve device efficiencies of white LECs. (C) 2013 Elsevier B.V. All rights reserved.
Improving the balance of carrier mobilities of host-guest solid-state light-emitting electrochemical cells
(2012)
Liao, Chih-Teng
;
Chen, Hsiao-Fan
;
Su, Hai-Ching
;
Wong, Ken-Tsung
;
照明與能源光電研究所
We report efficient host-guest solid-state light-emitting electrochemical cells (LECs) utilizing a cationic terfluorene derivative as the host and a red-emitting cationic transition metal complex as the guest. Carrier trapping induced by the energy offset in the lowest unoccupied molecular orbital (LUMO) levels between the host and the guest impedes electron transport in the host-guest films and thus improves the balance of carrier mobilities of the host films intrinsically exhibiting electron preferred transporting characteristics. Photoluminescence measurements show efficient energy transfer in this host-guest system and thus ensure predominant guest emission at low guest concentrations, rendering significantly reduced self-quenching of guest molecules. EL measurements show that the peak EQE (power efficiency) of the host-guest LECs reaches 3.62% (7.36 lm W(-1)), which approaches the upper limit that one would expect from the photoluminescence quantum yield of the emissive layer (similar to 0.2) and an optical out-coupling efficiency of similar to 20% and consequently indicates superior balance of carrier mobilities in such a host-guest emissive layer. These results are among the highest reported for red-emitting LECs and thus confirm that in addition to reducing self-quenching of guest molecules, the strategy of utilizing a carrier transporting host doped with a proper carrier trapping guest would improve balance of carrier mobilities in the host-guest emissive layer, offering an effective approach for optimizing device efficiencies of LECs.
Influences of Structural Modification of S,N-Hexacenes on the Morphology and OFET Characteristics
(2019-06-19)
Huang, Yi-Fan
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Wang, Chun-Kai
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Lai, Bo-Han
;
Chung, Chin-Lung
;
Chen, Chin-Yi
Although chemical modifications on conjugated molecules are widely applied for the purpose of improving processability and device performances, the effect of the modification was far less investigated. Here, five S,N-hexacenes are studied to reveal the influences of (1) the lateral alkyl chain, (2) the terminal group (thiophene vs benzene), and (3) the end capping phenyl group of the hexacenes on the morphology and organic field-effect transistor (OFET) performances. Crystal arrays of the hexacenes were prepared via polydimethylsiloxane (PDMS)-assisted crystallization (PAC) prior to morphological and OFET characterizations. The lattice structures and crystal quality of the hexacenes were evaluated by microscopy and diffraction techniques including single-crystal diffractometer, electron diffraction, and grazing incidence wide-angle X-ray scattering. The systematic analyses led to the following conclusions: (1) the bulkier alkyl side chain assists to form more densely packed crystals with less structural defects; (2) the terminal thiophene rings bring about higher-lying E-HOMO, more ordered phase, and crystal orientation, whereas the terminal benzene rings deteriorate the structural order of the active layer and result in the liquid crystal phase; and (3) the phenyl end caps ameliorate the morphological order, intermolecular overlapping, thermal stability and elevate E-HOMO. Thus, EH-DTPTt-Ph delivers the highest mu(h), contributing to high-lying E-HOMO, well-oriented crystal array with a longer correlation length, and suitable lattice orientation. This systematic research provides the aspects about the effects of the functionalized S,N-hexacenes on the morphology and OFET characteristics, which is anticipated to be useful for the molecular design of heteroacenes.
Laser-Scanned Programmable Color Temperature of Electroluminescence from White Light-Emitting Electrochemical Cells
(2016-11-23)
Lee, Hsiao-Chin
;
Chiang, Chien-Ming Fan
;
Wu, Po-Yi
;
Yao, Yung-Chi
;
Sarma, Monima
Recently, the control of correlated color temperature (CCT) of artificial solid-state white-light sources starts to attract more attention since CTs affect human physiology and health profoundly. In this work, we proposed and demonstrated a method that can widely tune the CCTs of electroluminescence (EL) from white-light-emitting electrochemical cells (LECs) by employing plasmonic filters. These integrated on-chip plasmonic filters are composed of semicontinuous thin Ag film or Ag nanoparticles (NPs) both included in the indium tin oxide anode contact, which have different characteristics of plasmonic resonant absorptions that can tune the EL spectra of white LECs. The CCTs of EL from white LECs integrated with semicontinuous thin Ag film and randomly distributed Ag NPs are 5778 and 2350 K, respectively. A commercially available laser scanning system was used to locally thermal anneal the semicontinuous thin Ag film to form the randomly distributed Ag NPs on the scanned areas. Hence, these two kinds of filters can be integrated on the same chip of white LEC, giving more freedom to control the CCTs of white EL and more potential applications. In addition, the laser scanning system used here is quite often used in display manufactures so that our proposed method can be immediately adopted by the light-emitting diode industry.