Interface and thickness tuning for blade coated small-molecule organic light-emitting diodes with high power efficiency

Chang, Yu Fan; Chiu, Yu Chian; Chang, Hsien‐Ming; Wang, Yi Siang; Shih, Yi Lun; Wu, Chih Hao; Liu, Yi Lun; Lin, Yun-Hsuan; Meng, Hsin‐Fei; Chi, Yun; Huang, Hsiu-Lin; Tseng, Mei-Rurng; Lin, Huey-Wen; Zan, Hsiao‐Wen; Horng, Sheng Fu; Juang, Jenh‐Yih

doi:10.1063/1.4821881

Cited by 13 publications

(5 citation statements)

References 11 publications

(12 reference statements)

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“…In the present study, heptane gave the best results, i.e., the most homogeneous and smooth films (Figure 1). For chlorobenzene, homogeneous films are obtained when deposited at RT and 50 • C. Chlorobenzene is the most common solvent for organic compounds, for either spin coating or doctor blade technique; in many reports, both the solution and substrate need to be heated at 30-70 • C before deposition [21][22][23][24][25]. The temperature is commonly used to induce solvent evaporation.…”

Section: Resultsmentioning

confidence: 99%

Solvent Effect on Small-Molecule Thin Film Formation Deposited Using the Doctor Blade Technique

et al. 2023

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Small molecule thin films are the core of some organic optoelectronic devices. Their deposition by solution processes is an advantage for device fabrication and can be achieved via spin coating for small areas and slot-die or doctor blade for larger areas. Solution deposition of small molecule thin films is usually processed only with medium polarity solvents. Herein, the use and influence of solvents with several polarities and physicochemical properties to form small-molecule homogeneous thin films via the doctor blade technique over an area of 25 cm2 have been explored. Solvents with different polarity, heptane, chlorobenzene, N,N-dimethylformamide, acetonitrile, and methanol were used along with different deposition temperatures, from room temperature up to near the boiling temperature for each solvent. With heptane and chlorobenzene, smooth films with an average roughness of 3 nm and thickness of 100–120 nm were obtained. The film was homogeneous over the whole substrate for temperatures from room temperature to close to the boiling temperature of both solvents. On the other hand, with dimethylformamide, a film is observed when the deposition is conducted only at room temperature; when the deposition temperature increases, the formation of agglomerates of several sizes from 1 to 5 nm was observed. With acetonitrile, and methanol, no films were formed, and only nanoaggregates were created on the substrate due to the solvent high vapor pressure, and the agglomerate size depends on the deposition temperature. The measure of the contact angle of pure solvent and solutions indicated that wettability helps to film formation over the whole substrate. For heptane and chlorobenzene, a small angle was measured; meanwhile, the contact angle is large in acetonitrile leading to the formation of nanoaggregates. In the case of methanol solution, although it wets very well, no film is deposited because it has high volatility.

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Section: Resultsmentioning

confidence: 99%

Solvent Effect on Small-Molecule Thin Film Formation Deposited Using the Doctor Blade Technique

et al. 2023

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“…Kido and co-workers proposed the bipolar host material 2,6-bis(3-(9 H -carbazol-9-yl)phenyl)pyridine (DCzPPy) with high triplet energy and carrier mobilities; upon doping with the phosphor emitter, iridium(III) bis(4,6-(difluorophenyl)pyridinato-N,C2′)picolinate (FIrpic), a vacuum-deposited blue phosphorescent OLED was obtained with a high efficiency and only slight efficiency roll-off . However, because of the deep highest occupied molecular orbital (HOMO) level of DCzPPy, an additional hole transport layer (HTL) with a suitable HOMO level was proposed in the device structure to promote hole injection. − We also used DCzPPy as the host and 9-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]- N , N , N ′, N ′-tetraphenyl-9 H -carbazole-3,6-diamine (DACT-II) as the guest to fabricate the green emission TADF-OLED . In this device, we proposed a novel double-cross-linked HTL composed of N , N ′-bis(4-(6-((3-ethyloxetan-3-yl)methoxy))-hexylphenyl)- N , N ′-diphenyl-4,4′-diamine and N , N -bis(4-(6-((3-ethyloxetan-yl)methoxy)hexyloxy)phenyl)-3,5-di(9 H -carbazol-9-yl)benzenamine (Oxe-DCDPA) coated on top of PEDOT:PSS to form three stepwise increased HOMO levels for improving hole current injection as well as preventing exciton quench.…”

Section: Introductionmentioning

confidence: 99%

Highly Efficient Solution-Processed Thermally Activated Delayed Fluorescence Bluish-Green and Hybrid White Organic Light-Emitting Diodes Using Novel Bipolar Host Materials

Ngo

Hung

Tsai

et al. 2019

ACS Appl. Mater. Interfaces

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Two pyridine-containing bipolar host materials with high triplet energy, 9,10-dihydro-9,9-dimethyl-10-(3-(6-(3-(9,9-dimethylacridin-10(9H)-yl)phenyl)pyridin-2-yl)phenyl acridin (DDMACPy) and N-(3-(6-(3-(diphenyl amino)phenyl)pyridin-2-yl)phenyl)-N-phenylbenzenamine (DTPAPy), are synthesized from the modification of the commonly adapted host material 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine (DCzPPy). The highest occupied molecular orbital levels of DDMACPy (5.50 eV) and DTPAPy (5.60 eV) are found to be shallower than that of DCzPPy (5.90 eV) that leads to the improvement in hole injection from the hole transport layer PEDOT:PSS (WF = 5.10 eV). These host materials are used in the emitting layer of bluish-green organic light-emitting diode (OLED) with the thermally activated delayed fluorescence (TADF) emitter, 9,9-dimethyl-9,10-dihydroacridine-2,4,6-triphenyl-1,3,5-triazine, as the guest. The DDMACPy-based device shows the highest performance among them, with the maximum external quantum efficiency (EQEmax), current efficiency (CEmax), and power efficiency (PEmax) of 21.0%, 53.1 cd A–1, and 44.0 lm W–1 at CIE (0.17, 0.42), respectively. By further doping with the red-emitting phosphor iridium(III) bis(2-phenylquinoline)(2,2,6,6-tetramethylheptane-3,5-ionate) [Ir(dpm)PQ2] and yellow-emitting phosphor iridium(III) bis(4-(4-t-butylphenyl)thieno[3,2-c]pyridinato-N,C20)acetylacetonate (PO-01-TB) emitters into the bluish-green emitting layer, a TADF–phosphor hybrid white OLED (T–P WOLED) is obtained with excellent EQEmax, CEmax, and PEmax of 17.4%, 48.7 cd A–1, and 44.5 lm W–1 at CIE (0.35, 0.44), respectively. Moreover, both the bluish-green and WOLED show a low efficiency roll-off with external quantum efficiencies at the brightness of 1000 cd m–2 (EQE1000) of 18.7 and 16.2%, respectively, which are the highest performance records among the solution-processed TADF bluish-green and T–P WOLEDs.

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“…The details were similar to blade coating of organic layers and were reported elsewhere. [16][17][18][19][20][21][22][23] Smooth and uniform IGZO film can be obtained from blade speed below certain values. 24 In FIG.…”

Section: A Device Performancementioning

confidence: 99%

Blade-coated sol-gel indium-gallium-zinc-oxide for inverted polymer solar cell

et al. 2016

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The inverted organic solar cell was fabricated by using sol-gel indium-gallium-zinc-oxide (IGZO) as the electron-transport layer. The IGZO precursor solution was deposited by blade coating with simultaneous substrate heating at 120 °C from the bottom and hot wind from above. Uniform IGZO film of around 30 nm was formed after annealing at 400 °C. Using the blend of low band-gap polymer poly[(4,8-bis-(2-ethylhexyloxy)-benzo(1,2-b:4,5-b’)dithiophene)-2,6-diyl-alt- (4-(2-ethylhexanoyl)-thieno [3,4-b]thiophene-)-2-6-diyl)] (PBDTTT-C-T) and [6,6]-Phenyl C71 butyric acid methyl ester ([70]PCBM) as the active layer for the inverted organic solar cell, an efficiency of 6.2% was achieved with a blade speed of 180 mm/s for the IGZO. The efficiency of the inverted organic solar cells was found to depend on the coating speed of the IGZO films, which was attributed to the change in the concentration of surface OH groups. Compared to organic solar cells of conventional structure using PBDTTT-C-T: [70]PCBM as active layer, the inverted organic solar cells showed significant improvement in thermal stability. In addition, the chemical composition, as well as the work function of the IGZO film at the surface and inside can be tuned by the blade speed, which may find applications in other areas like thin-film transistors.

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Interface and thickness tuning for blade coated small-molecule organic light-emitting diodes with high power efficiency

Cited by 13 publications

References 11 publications

Solvent Effect on Small-Molecule Thin Film Formation Deposited Using the Doctor Blade Technique

Solvent Effect on Small-Molecule Thin Film Formation Deposited Using the Doctor Blade Technique

Highly Efficient Solution-Processed Thermally Activated Delayed Fluorescence Bluish-Green and Hybrid White Organic Light-Emitting Diodes Using Novel Bipolar Host Materials

Blade-coated sol-gel indium-gallium-zinc-oxide for inverted polymer solar cell

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