Browsing by Author "Chen, Chin-Ti"

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Achieving high-efficiency non-doped blue organic light-emitting diodes: charge-balance control of bipolar blue fluorescent materials with reduced hole-mobility
(2009)
Chi, Chih-Chin
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Chiang, Chih-Long
;
Liu, Shun-Wei
;
Yueh, Han
;
Chen, Chin-Ti
We found an unusual way in improving electroluminescence efficiency of blue organic light-emitting diodes (OLEDs). Two electron deficient 4,5-diazafluorene- or di(2,2'-pyridyl)-containing blue fluorophores, PhSP(N2)DPV (4,5-diaza-2'-diphenylamino-7'-(2,2"-diphenylvinyl)-9,9'-spirobifluorene) and PhF(py2)DPV (N-[7-(2,2- diphenylvinyl)- 9,9'-di(2,2"-pyridyl)-2-fluorenyl]-N,N-diphenylamine), were synthesized and characterized for non-doped blue OLEDs. Whereas PhF(py2)DPV OLED performs ordinarily, PhSP(N2)DPV OLED outperforms previously known PhSPDPV (2-diphenylamino-7-diphenylvinyl-9,9'-spirobifluorene) OLED significantly: maximum external quantum efficiency of similar to 5% (4.6% at 20 mA cm(-2)) and the peak electroluminance of 60510 cd m(-2) (1810 cd m(-2) at 20 mA cm(-2)) versus 3.4% (2.9% at 20 mA cm(-2)) and 33020 cd m(-2) (910 cd m(-2) at 20 mA cm(-2)) of PhSPDPV OLED. We attribute the superior performance of PhSP(N2)DPV OLED to the good charge balancing, which is in turn due to the very low hole mobility of PhSP(N2)DPV. The experimental results reveal that the electron-deficient moiety, 4,5-diazafluorene or di(2,2'-dipyridyl), increases electron affinity but reduces the hole mobility. Electron mobility, determined by time-of-flight (TOF) method, is 5 x 10(-5) and 5 x 10(-4) cm(2) V(-1) s(-1) (at an electric field of 4.9 x 10(5) V cm(-1)) for PhSP(N2)DPV and PhF(py2)DPV, respectively. Surprisingly, they are not higher than 8 x 10(-4) cm(2) V(-1) s(-1) of nonpolar PhSPDPV. On the other hand, hole mobility is 2 x 10(-6) and 2 x 10(-4) cm(2) V(-1) s(-1) for PhSP(N2)DPV and PhF(py2)DPV, respectively, and they are both significantly lower than 6 x 10(-3) cm(2) V(-1) s(-1) of PhSPDPV. For PhSP(N2)DPV and PhF(py2)DPV bipolar blue fluorophores, we have demonstrated that electron-transporting and light-emitting functions involve different molecular halves. The design of such molecular halves greatly facilitates the optical and electronic optimizations of fluorophores for high-performance OLEDs.
Anode interlayer in organic photovoltaics: Narrow bandgap small molecular materials as exciton-blocking layer
(2019-11-01)
Golder, Jan
;
Lin, Chiao-Wen
;
Chen, Chin-Ti
;
應用化學系
;
Department of Applied Chemistry
Six materials were used as an interlayer at the anode side (anode interlayer [AIL]) of an archetypical planar heterojunction organic solar cell (OSC). In addition to two conventional wide bandgap hole transport materials (HTMs), tris(4-carbazol-9-ylphenyl)amine (TCTA) and trans-4,4 '-bis[N-(naphthalen-1-yl)-N-phenylamino]stilbene (NPAE), we explore four narrow bandgap materials, bis(biphenylaminospiro)-fumaronitrile (PhSPFN), bis(N-(naphthalen-1-yl)-N-phenylamino)anthraquinone (NPAAnQ), bis-(di(2-fluorophenyl)aminospiro)-fumaronitrile (FPhSPFN), and bis[4-(N-(pyren-1-yl)-N-phenylamino)phenyl]fumaronitrile (PyPAFN), the energy levels of which essentially align with the ones of SubPc, the active light-absorbing material of the OSC study herein. By using a narrow bandgap AIL, universally enhanced short-circuit current density and power conversion efficiencies (PCEs) have been achieved. In addition, one of these materials, FPhSPFN, results in a PCE of 5.13%, which is the highest reported value for SubPc solar cells with a similar architecture. This is ascribed to the formation of an otherwise passive exciton-blocking interface. Furthermore, this demonstrates that charge selectivity by way of a high-lying lowest unoccupied molecular orbital (LUMO) energy level is not a prerequisite for successful AIL design. As such, in terms of energy level alignment and bandgap energies, we establish a viable alternative approach toward interface and interlayer material design.
Facile Solution Dropping Method: A Green Process for Dyeing TiO2 Electrodes of Dye-Sensitized Solar Cells with Enhanced Power Conversion Efficiency
(2015-01-01)
Yeh, Shih-Chieh
;
Lee, Pei-Heng
;
Liao, Hua-Yang
;
Chen, Yu-You
;
Chen, Chin-Ti
A simple solution dropping method was established for sensitizing TiO2 in the fabrication of dye-sensitized solar cells (DSCs). As compared with the conventional immersion dyeing process, this solution dropping method is very fast, taking less than similar to 5 min vs >5-10 h typically required in the traditional immersion dyeing process. There is much less organic solvent and dye substance (95% less) used in the dyeing TiO2 process and hence significantly less disposal of chemical wastes from device fabrications. Therefore, this facile solution dropping method is a greener process than the immersion dyeing process. Moreover, the solution dropping method is superior to the immersion dyeing process in terms of power conversion efficiency (PCE) of the device. We have acquired compelling evidence through dye uptake assessment of TiO2 electrodes, depth profile assay by SEM-EDX, and charge dynamic characteristics from transient photovoltage/photocarrent analysis indicating that the elevated dye loading level of a TiO2 electrode is the main cause responsible for increasing short-circuit current and hence the PCE of DSCs. Three types of dye were used in this study to demonstrate the superiority of the solution dropping method, including classical N719 (a ruthenium transition metal complex), 1P-PSS (a metal free organic dye), and newly synthesized ATT (a beta-pyrrole carbon-conjugated zinc tetraphenylporphyrin). Using the solution dropping method, dye uptake was improved from 3.0 X 10(-7) to 9.9 X 10(-7) mole cm(-2), 5.3 X 10(-7) to 6.6 X 10(-7) mole cm(-2), and 4.7 X 10(-8) to 3.92 X 10(-7) mole cm(-2) for N719, 1P-PSS, and ATT, respectively. In addition, the PCEs, averaged from 30 or 40 tested devices each with a 0.4 cm X 0.4 cm active area, were all improved from 8.1% to 8.5%, 5.9% to 6.6%, and 4.196 to 6.7% for N719, 1P-PSS, and ATT, respectively.
General application of blade coating to small-molecule hosts for organic light-emitting diode
(2014-10-01)
Chang, Hao-Wen
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Lee, Yi-Ting
;
Tseng, Mei-Rurng
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Jang, Meng-Hao
;
Yeh, Han-Cheng
Blade coating is applied to multi-layer phosphorescent OLED with five small-molecule hosts for the emission layer, including bis[3,5-di (9H-carbazol-9-yl)phenyl]diphenylsilane (SimCP2), 2,6-bis(3-(9H-carbazol-9-yl)phenyl) pyridine (26DCzPPy), 4,4\',4 \'\'-tris-(N-carbazolyl)-triphenylamine (TCTA), 9,9-bis[4-(3,6-di-tert-butylcarbazol-9-yl)phenyl]fluorene (TBCPF), and 2,7-bis(diphenylphosphoryl)-9,9\'-spirobi[fluorene] (SPPO13). In general, blade coating gives low surface roughness around 0.2 nm without phase separation of the emitter and the host. In the large area of 2 cm by 3 cm the film thickness distribution is within 10% and uniform light-emission is achieved. 1,3-Bis[2-(4-tert-butylphenyl)-1,3,4-oxadiazo-5-yl]benzene (OXD-7) is added to tune the electron transport. Among all the hosts, 26DCzPPy and SimCP2 have by far the best electron hole balance and consequently show the highest efficiency. For SimCP2, the maximal efficiency is 15.8 cd/A for blue and 24.2 cd/A for white emission. The order of efficiencies for the hosts is found to be quite different from the order in vacuum evaporation for the same device structures. (C) 2014 Elsevier B.V. All rights reserved.
High performance hybrid white OLEDs based on new platinum complexes and new blue fluorescence host
(2014-01-01)
Poloek, Anurach
;
Wang, Chieh
;
Lin, Chiao-Wen
;
Chen, Chin-Ti
;
Chen, Chao-Tsen
A new series of platinum complexes containing 4-hydroxy-1,5-naphtyridine derivative with different substitutens such as methyl, dimethyl, phenyl, phenoxy, dimethyl amine, piperidine, morpholine, phenoxazine or carbazole unit as the primary ligand and 2-(2,4-difluorophenyl)pyridine as the secondary ligand were synthesized and characterized. Single crystal X-ray diffraction studies of FPtOPhND, FPtCzND and FPtdmaND showed trans-coordinated in distorted square-planar geometry. Their photophysical properties and electrochemical properties were examined. All platinum complexes in these series exhibited dual emissions not only in solution but also in solid state thin film. Employing CBP or 4P-NPD as host material, high efficiency monochromatic and high quality hybrid white organic light emitting diodes (WOLEDs) were achieved with the single platinum complex dopant device, a relatively simple device configuration.
Highly efficient red electrophosphorescent device incorporating a bipolar triphenylamine/bisphenylsulfonyl-substituted fluorene hybrid as the host
(2009)
Hsu, Fang-Ming
;
Chien, Chen-Han
;
Hsieh, Ya-Jou
;
Wu, Chen-Hao
;
Shu, Ching-Fong
We have fabricated highly efficient red phosphorescent organic light-emitting diodes (PHOLEDs) incorporating a bipolar host material, 2,7-bis(phenylsulfonyl)-9-[4-(N,N-diphenylamino)phenyl]-9-phenylfluorene (SAF), doped with 7 wt% tris(1-phenylisoquinolinolato-C(2),N)iridium(III) [Ir(piq)(3)]. Attaching the electron-donating (p-type) triphenylamine group onto the electron-accepting (n-type) 2,7-bis(phenylsulfonyl)fluorene segment (through the C9 position of the fluorene unit) imparts SAF with good morphological stability, high triplet energy gap (ET), bipolar transporting ability, and matching energy levels with adjacent carrier-transporting layers. Consequently, the SAF-based red-PHOLED exhibited a very low turn-on voltage (2.4 V) and high electroluminescence efficiencies of 15.8% and 22.0 lm W(-1), superior to those of the corresponding device incorporating a conventional host material, 4,4'-N,N'-dicarbazolbiphenyl (CBP; 3.2 V, 8.5%, and 8.4 lm W(-1), respectively). At a practical brightness of 1000 cd m(-2), the efficiencies of the SAF-based red-PHOLED remained high (13.1%, 14.4 lm W(-1)).
Hydroxynaphthyridine-Derived Group III Metal Chelates: Wide Band Gap and Deep Blue Analogues of Green Alq(3) (Tris(8-hydroxyquinolate)aluminum) and Their Versatile Applications for Organic Light-Emitting Diodes
(2009-01-21)
Liao, Szu-Hung
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Shiu, Jin-Ruei
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Liu, Shun-Wei
;
Yeh, Shi-Jay
;
Chen, Yu-Hung
A series of group III metal chelates have been synthesized and characterized for the versatile application of organic light-emitting diodes (OLEDs). These metal chelates are based on 4-hydroxy-1,5-naphthyridine derivates as chelating ligands, and they are the blue version analogues of well-known green fluorophore Alq(3) (tris(8-hydroxyquinolinato)aluminum). These chelating ligands and their metal chelates were easily prepared with an improved synthetic method, and they were facially purified by a sublimation process, which enables the materials to be readily available in bulk quantity and facilitates their usage in OLEDs. Unlike most currently known blue analogues of Alq(3) or other deep blue materials, metal chelates of 4-hydroxy-1,5-naphthyridine exhibit very deep blue fluorescence, wide band gap energy, high charge carrier mobility, and superior thermal stability. Using a vacuum-thermal-deposition process in the fabrication of OLEDs, we have successfully demonstrated that the application of these unusal hydroxynaphthyridine metal chelates can be very versatile and effective. First, we have solved or alleviated the problem of exciplex formation that took place between the hole-transporting layer and hydroxynaphthyridine metal chelates, of which OLED application has been prohibited to date. Second, these deep blue materials can play various roles in OILED application. They can be a highly efficient nondopant deep blue emitter: maximum external quantum efficiency (eta ext) of 4.2%; Commision Internationale de L'Eclairage x, y coordinates, CIE(x,y) = 0.15, 0.07. Compared with Alq(3), Bebqp(2) (beryllium bis(benzoquinolin-10-olate)), or TPBI (2,2',2 ''-(1,3,5-phenylene)tris(1-phenyl-1H-benzimidazole), they are a good electron-transporting material: low HOMO energy level of 6.4-6.5 eV and not so high LUMO energy level of 3.0 3.3 eV. They can be ambipolar and possess a high electron mobility of 10(-4) cm(2)/V s at an electric field of 6.4 x 10(5) V/cm. They are a qualified wide band gap host material for efficient blue perylene (CIE(x,y) = 0.14, 0.17 and maximum (eta ext) 3.8%) or deep blue 9,10-diphenylanthracene (CIE(x,y) = 0.15, 0.06 and maximum (eta ext) 2.8%). For solid state lighting application, they are desirable as a host material for yellow dopant (rubrene) in achieving high efficiency ((eta ext) 4.3% and (eta P) 8.7 lm/W at an electroluminance of 100 cd/m(2) or (eta ext) 3.9% and (eta P) 5.1 lm/W at an electroluminance of 1000 cd/m(2)) white electroluminescence (CIE(x,y) = 0.30, 0.35).
Influence of molecular dipoles on the photoluminescence and electroluminescence of dipolar spirobifluorene
(2007-01-01)
Chiang, Chih-Long
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Tseng, Shih-Min
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Chen, Chin-Ti
;
Hsu, Chao-Ping
;
Wen, Yuh-Sheng
Here we study a series of strongly fluorescent spirobifluorene compounds, red PhSPDCV and blue PhSPDPV, together with their spiro "dimer" analogs, BisPhSPDCV and blue BisPhSPDPV. We found that the fluorescence quantum yield as well as the OLED performance of the strongly dipolar red PhSPDCV decrease significantly in the "dimeric" analog BisPhSPDCV, but not in the weakly dipolar PhSPDPV and BisPhSPDPV. On the other hand, by doping the highly dipolar PhSPDCV to an isolated environment having low polarity Alq3 as the host matrix and avoiding the emission-quenching dipole from the neighboring molecules, very high performance of saturated yellow OLEDs has been obtained as well.
Influence of molecular dipoles on the photoluminescence and electroluminescence of dipolar spirobifluorenes
(2008-01-24)
Chiang, Chih-Long
;
Tseng, Shih-Min
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Chen, Chin-Ti
;
Hsu, Chao-Ping
;
Shu, Ching-Fong
This Full Paper investigates a series of strongly fluorescent donor-acceptor-substituted spirobifluorene compounds, red 2-diphenylamino-7-(2,2-dicyanovinyl)-9,9'-spirobifluorene (DCV), green 2-diphenylamino-9,9'-spirobifluorene7-carxoxaldehyde (CHO), and blue 2-diphenylamino-7-(2,2-diphenylvinyl)-9,9'-spirobifluorene (DPV), together with their spiro-linked "dimeric" analogs, 2DCV, 2,2'-bis(diphenylamino)-9,9'-spirobifluorene-7,7'-dicarboxaldehyde (2CHO), and 2,2'-bis(diphenylamino)-7,7'bis(2,2-diphenylvinyl)-9,9'-spirobifluorene (2DPV), respectively. The emission optical density and, hence, the intensity of photoluminescence (PL) or electroluminescence (EL) of the "dimeric" analogs is presumed to increase, which is beneficial for organic light-emitting diode (OLED) applications. The physical properties, including the dipole moments obtained from quantum chemistry calculations, emission solvatochromism, fluorescence quantum yield (Of) as well as the EL of these six spirobifluorene compounds have been examined in detail. We found that Of as well as OLED performance (EL efficiency and intensity) of the strongly dipolar DCV decrease significantly in the "dimeric" analog 2DCV, but less so in the moderately dipolar CHO and 2CHO, and only slightly in the weakly dipolar DPV and 2DPV. This is parallel to the intramolecular dipole moment, which is large for 2DCV, medium for 2CHO, and very small for 2DPV. Here, we show for the first time systematically that the luminescence intensity is closely correlated with the local electric field induced by the molecular dipole. A strong electric field may facilitate radiationless decay channels with a charge-transfer nature, leading to a high quenching rate. Consistent with this conclusion, which is derived from the red DCV/2DCV and green CHO/2CHO, our new blue fluorophore DPV with an essentially zero dipole moment has successfully achieved one of the best electrofluorescent blue OLEDs. At the same time, by doping the highly dipolar DCV into an isolated environment with the low-polarity Alq(3) as the host matrix, we obtained a very high performance of saturated yellow OLEDs as well, This is possibly due to the reduction of emission-quenching dipoles from the neighboring molecules. Our results have provided an important insight in designing luminescent materials, as follows: molecular dipole moments should be kept at a low magnitude to avoid quenching induced by a strong local electric field in the chromophore.
New platinum complexes exhibiting host dependent photoluminescence as single dopants in double emitting layer, voltage independent hybrid white electroluminescence devices
(2015-01-01)
Poloek, Anurach
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Wang, Chieh
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Chang, Yung-Ting
;
Lin, Chiao-Wen
;
Chen, Chao-Tsen
Four heteroleptic platinum complexes (FPtXNDs) bearing 4-hydroxy-1,5-naphthyridine (XND) derivatives functionalized with phenyl (X = Ph), dimethylamino (X = dma), morpholino (X = mor), or phenoxazino (X = pxz) units as one ligand and 2-(2,4-difluorophenyl) pyridine (F) as the other common ligand were newly synthesized and characterized. Each platinum complex has absorption and photoluminescence (PL) spectroscopic characteristics. As demonstrated by X-ray crystallography (of FPtdmaND and FPtpxzND), electrochemical and theoretical studies, the unusual spectroscopic features of FPtpxzND (such as its weak absorption band around 450-600 nm, its significant concentration dependent solution PL wavelength but low host dependent thin film PL wavelength (which is relatively long) and its particularly low solution PL quantum yield (Phi(PL))) the relatively strong absorption of FPtdmaND and FPtmorND, and the relatively long PL wavelength of FPtPhND have been reasonably explained. After each platinum complex had been examined for monochromatic organic lightemitting diodes (OLEDs), having a relatively high FPL as well as an appropriate greenish yellow PL in the monomeric form and an orange to red PL in the aggregate/excimeric form, FPtdmaND and FPtmorND have been chosen as dopant materials in the construction of single or double emitting layer (EML) hybrid white organic light-emitting diodes (OLEDs). A high performance warm white electroluminescence (EL) (CIEx,y (0.42-0.43, 0.43-0.44)) was obtained where the same platinum complex dopant FPtdmaND was doped (5 or 8 wt%) in two EMLs, 4,4\'-di(9H-carbazol-9-yl)-1,1\'-biphenyl (CBP) harvesting monomeric emission and the highly fluorescent blue N,N\'-di-1-naphthalenyl-N,N\'-diphenyl-[1,1\':4\',1 \'\':4 \'\',1\'\'\'-quaterphenyl]-4,4\'\'\'-diamine (4P-NPD) harvesting excimer/aggregate emission. This warm white EL showed a high colour rendering index (CRI) of 86-88, and a reasonably good EL efficiency of 9.7%, 22.5 cd A(-1), or 10.7 lm W-1. EL with improved white chromaticity (CIEx,y (0.37-0.39, 0.39-0.41)) can be obtained using FPtmorND as the single dopant, although it has a somewhat inferior CRI (84-86) and EL efficiency (8.3%, 20.1 cd A(-1), or 9.5 lm W-1). Nevertheless, both double EML hybrid white OLEDs exhibit a rather constant CRI and CIEx,y under a driving voltage between 7 and 10 V.
Novel carbazole/fluorene hybrids: Host materials for blue phosphorescent OLEDs
(2006-06-22)
Shih, Ping-I
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Chiang, Chih-Long
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Dixit, Ajay Kumar
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Chen, Ching-Kun
;
Yuan, Mao-Chuan
A series of carbazole/fluorene (CBZm-Fn) hybrids were effectively synthesized through Friedel-Crafts-type substitution of the carbazole rings. These compounds were thermally and morphologically stable host materials for OLED applications. Efficient blue phosphorescent OLEDs were obtained when employing CBZ1-F2 as the host and Firpic as the guest.
Oligothiophenes and alkyl side-chain arrangement the structure-property study of their diketopyrrolopyrrole copolymers for organic photovoltaics
(2018-10-01)
Wu, Jhao-Lin
;
Lin, Chiao-Wen
;
Golder, Jan
;
Lin, Tsu-Wei
;
Chen, Chin-Ti
We have synthesized and characterized a series of diketopyrrolopyrrole (DPP)-oligothiophene copolymers, of which the number of regioregular oligothiophene ring (2T, 3T and 4T) and the arrangement of the alkyl side-chain on regioirregular quarterthiophene (4T0, 4T1 and 4T2) are variable. The side chains with regioregular lead to more planar copolymer backbones and higher short circuit current (J(sc)), but backbone torsion (due to regioirregular side chains) generates greater open-circuit voltages (V-OC) for DPP-oligothiophene copolymers. The increasing thiophene ring progressively raises HOMO energy level of copolymers but marginally affects their band gaps. Additionally, the HOMO energy level was found declined significantly with side-chain regioirregularity, because of reducing length of pi-conjugation. The HDDPP4T0 exhibits the strongest absorption, extensive network structure, and high hole mobility (mu(h )= 6.04 x 10(-4)cm(2)V(-1) s(-1)). These characteristics contribute to the exceptional high J(SC) of 18.96 mA/cm(2) for OPV with PCE = 6.12%. However, the HDDPP4T1 having an optimal combination of pi-conjugation and energy level affords the second highest V-OC (0.73 V) and the third highest J(SC) (16.89 mA/cm(2)), resulting the best PCE of 7.51% among all. X-ray scattering, transmission electron microscopy, atomic force microscopy, and space-charge-limited-current (SCLC) measurements reveal that the solvent additive of diphenylether (DPE) enables PC71BM-blended copolymers thin film in crystallinic fibril with enhanced hole mobility.
Oxasmaragdyrins as New and Efficient Hole-Transporting Materials for High-Performance Perovskite Solar Cells
(2017-09-20)
Mane, Sandeep B.
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Sutanto, Albertus Adrian
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Cheng, Chih-Fu
;
Xie, Meng-Yu
;
Chen, Chieh-I
The high performance of the perovskite solar cells (PSCs) cannot be achieved without a layer of efficient hole-transporting materials (HTMs) to retard the charge recombination and transport the photogenerated hole to the counterelectrode. Herein, we report the use of boryl oxasmaragdyrins (SM01, SM09, and SM13), a family of aromatic core-modified expanded porphyrins, as efficient hole-transporting materials (HTMs) for perovskite solar cells (PSCs). These oxasmaragdyrins demonstrated complementary absorption spectra in the low-energy region, good redox reversibility, good thermal stability, suitable energy levels with CH3NH3PbI3 perovskite, and high hole mobility. A remarkable power conversion efficiency of 16.5% (V-oc= 1.09 V, J(sc) = 20.9 mA cm(-2), fill factor (FF) = 72%) is achieved using SM09 on the optimized PSCs device employing a planar structure, which is close to that of the state-of-the-art hole-transporting materials (HTMs), spiro-OMeTAD of 18.2% (V-oc = 1.07 V, J(sc) = 22.9 mA cm(-2), FF = 74%). In contrast, a poor photovoltaic performance of PSCs using SM01 is observed due to the interactions of terminal carboxylic acid functional group with CH3NH3PbI3.
Polymer side-chain substituents elucidate thermochromism of benzodithiophene-dithiophenylacrylonitrile copolymers - polymer solubility correlation of thermochromism and photovoltaic performance
(2017-06-28)
Chen, Hung-Yang
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Lin, Chiao-Wen
;
Chen, Chin-Ti
;
Chen, Chao-Tsen
;
Golder, Jan
Nine pBCNx polymers based on a donor-p-acceptor benzo[1,2-b:4,5-b']dithiophene-(E)-2,3-di(thiophen-2-yl) acrylonitrile main-chain structure and n-octyl/2-ethylhexyl as the side-chain substituents have been designed and synthesized. The thermochromism of the pBCNx polymers has been carefully examined in both solution and the thin-film state. With additional evidences from Raman spectroscopy and AFM microscopy, we have deciphered the varied colours of nine pBCNx polymers in solution and the pronounced thin-film thermochromism only observed for certain pBCNx polymers, i.e., pBCN4, pBCN5, pBCN6, and pBCN8. The alkyl side-chain, and hence the solubility or aggregation of pBCNx polymers, is a main factor of the varied colour in solution and the varied thermochromism in the thin film. We have identified that a stronger main-chain and main-chain interaction are present on the (E)-2,3-di(thiophen-2-yl) acrylonitrile moiety, whereas the poor to moderate solubility pBCN3, pBCN5', and pBCN7 exhibit pronounced thermochromism in solution, and pBCN4, pBCN5, pBCN6, and pBCN8 are four polymers which have good solubility in solution and show thermochromism in the thin-film state. We took navy blue pBCN3 (poor solubility), magenta pBCN4 (good solubility), and reddish purple pBCN5' (moderate solubility) for the fabrication of bulk heterojunction organic photovoltaics (OPVs). With a solvent annealing treatment, the power conversion efficiency of the OPVs has been improved significantly from 4.7% to 6.2% for the good solubility pBCN4, but there is little and no improvement for the moderate solubility pBCN5' and poor solubility pBCN3, respectively. Our study verifies that the good OPV performance of the pBCNx polymers can be correlated to the pronounced thin-film thermochromism. A good solubility of the polymer is a common characteristic of a material with significant thin-film thermochromism and good OPV performance.
Red Fluorenes as the efficient host emitter for non-doped red organic light-emitting diodes
(2005)
Chiang, Chih-Long
;
Wu, Min-Fei
;
Shu, Ching-Fong
;
Chen, Chin-Ti
;
應用化學系
Crystallinic red fluorophores based on donor-acceptor substituted spirofluorene, i.e., PhSPDCV show strong fluorescence in solution (phi(f) similar to 70%) as well as in solid state (phi(f) > 30%). Non-doped red OLEDs fabricated with PhSPDCV exhibit Authentic red (CIE, x = 0.65, y = 0.35) electroluminescence with brightness over 12,000 cd m(-2) (or > 600 cd m(-2) at 20 mA cm(-2)) and remarkable external quantum efficiency as high as 3.6%. On the other hand, the bis-substituted derivatives of spirofluorene BisPhSPDCV show relatively weak fluorescence both in solution (phi(f) < 20%) and in solid state (phi(f) < 10%). Although saturated red electroluminescence (CIE, x = 0.65, y = 0.35) is observed, non-doped red OLED containing BisPhSPDCV exhibit much worse performance compared with that of PhSPDCV OLEDs.
SimCP3-An Advanced Homologue of SimCP2 as a Solution-Processed Small Molecular Host Material for Blue Phosphorescence Organic Light-Emitting Diodes
(2016-10-01)
Lee, Yi-Ting
;
Chang, Yung-Ting
;
Wu, Cheng-Lung
;
Golder, Jan
;
Chen, Chin-Ti
We have overcome the synthetic difficulty of 9,9',9 '',9 ''',9 '''',9 '''''-((phenylsilanetriyl) tris(benzene-5,3,1-triyl))hexakis(9H-carbazole) (SimCP3) an advanced homologue of previously known SimCP2 as a solution-processed, high triplet gap energy host material for a blue phosphorescence dopant. A series of organic light-emitting diodes based on blue phosphorescence dopant iridium (III) bis(4,6-difluorophenylpyridinato) picolate, FIrpic, were fabricated and tested to demonstrate the validity of solution-processed SimCP3 in the device fabrication.
Solid state molecular packing and photoluminescence of platinum complexes based on 1,5-naphthyridin-4-plate ligands
(2015-01-01)
Chen, Chin-Ti
;
Poloek, Anurack
;
Wang, Chieh
;
Lin, Chiao-Wen
;
Chen, Chao-Tsen
Solvent-assisted crystallization via a delayed-annealing approach for highly efficient hybrid mesoscopic/planar perovskite solar cells
(2017-12-01)
Sutanto, Albertus Adrian
;
Lan, Shiang
;
Cheng, Chih-Fu
;
Mane, Sandeep B.
;
Wu, Hui-Ping
The formation of a dense and uniform perovskite film with large grain is an important factor for getting excellent device performance. Here, we report an optimized solvent-assisted crystallization procedure followed by a delayed annealing for easy and reproducible fabrications of perovskite solar cells with a hybrid mesoscopic configuration. The working electrode contains a mesoporous TiO2 scaffold layer of 100 nm deposited on FTO substrate with a thin TiO2 blocking layer. The devices in this study were assembled using all commercially available materials without any extensive modification. Formation of uniform and pin-hole free perovskite nanocrystals with film thickness 200 nm on top of the scaffold layer was achieved via an optimized solvent assisted crystallization method. A much smoother perovskite layer was achieved with a delayed annealing for a certain period. The best performing device was obtained at the annealing delayed for 60 min, giving the power conversion efficiency 16.9% with an average value 15.4% obtained from 60 devices.
Structure-Property Relationship Study of Donor and Acceptor 2,6-Disubstituted BODIPY Derivatives for High Performance Dye-Sensitized Solar Cells
(2017-10-20)
Yeh, Shih-Chieh
;
Wang, Li-Jing
;
Yang, Hong-Ming
;
Dai, Yu-Huei
;
Lin, Chao-Wen
Seven donor and acceptor 2,6-disubstituted 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dyes have been synthesized and characterized. Including MPBTCA, which is a known compound, the seven BODIPY dyes have been characterized by varied physical methods, such as UV/Visible absorption spectroscopy, low energy photo-electron spectroscopy (AC-2), and HOMO-LUMO DFT/TDDFT calculation. All seven BODIPY dyes have absorption lambda(max) around 535-545 nm, which is significantly longer than 499 nm of 4,4-difluoro-1,3,5,7,8-pentamethyl-4-bora-3a,4a-diaza-s-indacene (PM 546). Having structural variation on donor group, acceptor group, donor pi-spacer, acceptor pi-spacer, and the substituent on boron, some BODIPY dyes exhibit small extinction coefficients or spectral integrals in solution (MPCtBTCA, MPBT-pyO, MPBTT-pyO, MTBTCA), broadening absorption spectral profile (MTBTCA), weak intramolecular charge transfer characteristics (MPBT-pyO, MPBTT-pyO, MTBTCA), too low LUMO energy level (PPBTCA), or insufficient dye-uptake by TiO2 FTO (MPBT-pyO, MPBTT-pyO, MTBTCA). Two of the seven BODIPY dyes, MPBTCA and MPBTTCA, do not show the adverse properties like other BODIPY dyes. With our improved TiO2 FTO (fluorine doped tin oxide) dyeing method, namely a solution dropping method, high performance dye-sensitized solar cells (DSCs) have been realized by MPBTCA and MPBTTCA photosensitizers. Power conversion efficiencies of 6.3 and 6.4% have been achieved by MPBTCA and MPBTTCA DSCs, respectively. To the best of our knowledge, MPBTCA and MPBTTCA are the most efficient dyes for the donor and acceptor 2,6-disubstituted BODIPY DSCs so far.
Synthesis and characterization of donor-acceptor-substituted fluorene fluorophores for non-doped red organic light emitting diodes
(2006-12-01)
Chiang, Chih-Long
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Wen, Ya-Ju
;
Wen, Yuh-Sheng
;
Shu, Ching-Fong
;
Chen, Chin-Ti
A series of fluorene fluorophores bearing bis(4-methoxyphenyl)amino electron donating substitutent as well as bisbenzothiazolylvinyl (AFDB), benzothiazolylcyanovinyl (AFCB), or dicyanovinyl (AFDC) electron accepting substituent were synthesized and characterized. A non-doped red organic light-emitting diode (OLED) device based on AFCB exhibited deep red (lambda(el)(max) = 670 nm, CIE, x = 0.65, y = 0.34) electroluminescence with brightness over 2380 cd/m(2) and an external quantum efficiency higher than 1.2%.