- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
High efficiency???low efficiency roll-off and long lifetime fluorescent white organic light-emitting diodes based on strategic management of triplet excitons via triplet-triplet annihilation up-conversion and phosphor sensitization
摘要： The simultaneous realization of high efficiency, low efficiency roll-off, long lifetime and stable electroluminescence (EL) spectra in fluorescent white organic light-emitting diodes (WOLEDs) is still a huge challenge. Here, we used a triplet-triplet annihilation up-conversion (TTA-UC) material as blue emission layer and phosphor sensitized fluorescent emitter as red emission layer and introduced a bipolar interlayer between them to fabricate high efficiency, low efficiency roll-off and long lifetime fluorescent WOLEDs. It is clearly seen that the bipolar interlayer not only efficiently distributed the singlet and triplet excitons, but also significantly stabilized the EL spectra. Thus, the resulting two-color fluorescent WOLEDs exhibited the maximum current efficiency (CE), power efficiency (PE) and external quantum efficiency (EQE) of 26.9 cd A-1, 22.3 lm W-1 and 12.8%, and remained 25.9 cd A-1, 16.9 lm W-1 and 12.1% at the luminance of 1000 cd m-2 and 23.1 cd A-1, 10.6 lm W-1 and 10.7% at the luminance of 10000 cd m-2, respectively, and the operational lifetime LT50 (50% decay, initial luminance of 1000 cd m-2) was also up to 984 h. It can be seen that these devices also showed stable EL spectra with Commission Internationale de I’Eclairage (CIE) of (0.51, 0.41) from 1000 cd m-2 to 5000 cd m-2 luminance. Furthermore, the fabricated three-color fluorescent WOLEDs by further introducing a green fluorescent emitter, also showed high efficiencies of 15.5 cd A-1, 13.0 lm W-1 and 8.1% and stable EL spectra with CIE of (0.43, 0.36) form 1000 cd m-2 to 5000 cd m-2 luminance. More importantly, their CE and EQE exhibited an increasing tendency with the luminance, a fully negligible efficiency roll-off. This design strategy provides a potential route towards high performance fluorescent WOLEDs.
关键词： fluorescent WOLEDs,bipolar interlayer,high efficiency,triplet-triplet annihilation up-conversion,phosphor sensitization,long lifetime,low efficiency roll-off
更新于2025-09-23 15:21:01
-
Investigation of electrical values of low-efficiency dye-sensitized solar cells (DSSCs)
摘要： Indium-tin-oxide (ITO)/density (d)- titanium dioxide (TiO2)/nonporous (nonp)-TiO2 is a TiO2-based bilayer photoanode. These photoanodes coated for dye-sensitized solar cells (DSSCs) were with nonp-TiO2 surface and had very thick ITO layer. DSSCs were fabricated with these photoanodes. After their current density-voltage (J-V) were analyzed, ?t was seen that they were low efficiency and the shape of their J-V curve was linear line instead of rectangle. In this study, it was examined the relationship between the dark current (IDC), the series resistance (Rs) and the shunt resistance (Rsh) were examined for evaluating the fill factor (FF) of low-efficiency DSSCs because of the photoanodes with nonp-TiO2 surfaces and very thick ITO for contact layer. It was seen in the J-V graph of DSSCs which had low FF value due to their IDC and low Rsh. The J-V graph of low-efficiency DSSCs is linear due to their low Rsh and high Rs values. Moreover, the too thick ITO layer decreases the resistance of photoanodes; however, electrons in these photoanodes can not efficiently transferred to external circuit from ITO contact layer of DSSCs.
关键词： Fill factor,Linear,Nonporous,Back electron,Low-efficiency,Dark current,Cell resistance
更新于2025-09-19 17:13:59
-
Efficient deep blue OLEDs with extremely low efficiency roll-off at high brightness based on phenanthroimidazole derivatives
摘要： Phosphorescent and thermally activated delayed fluorescence (TADF) emitters can break through the spin statistics rules and achieve great success in external quantum efficiency (over 5%). However, maintaining high efficiency at high brightness is a tremendous challenge for applications of organic light emitting diodes. Hence, we reported two phenanthroimidazole derivatives PPI-An-CN and PPI-An-TP and achieved extremely low efficiency roll-off with about 99% of the maximum external quantum efficiency (EQEmax) maintained even at a high luminance of 1000 cd/cm2 based non-doped devices. When doping the two materials in CBP (4,40-bis(N-carbazolyl)-1,10-biphenyl), the doped devices still exhibited excellent stability at high brightness with CIEy ≤ 0.07 and low turn-on voltage of only 2.8 V. The state-of-the-art low efficiency roll-off makes the new materials attractive for potential applications. It is first time that the Fragment Contribution Analysis method has been used to analyze the excited state properties of the molecules in the field of OLEDs, which helps us understand the mechanism more intuitively and deeply.
关键词： Fragment contribution analysis,Phenanthroimidazole,Deep blue,OLED,Low efficiency roll-off
更新于2025-09-16 10:30:52
-
Highly Efficient Solution-Processed TADF Bluish-Green and Hybrid White Organic Light-Emitting Diodes Using Novel Bipolar Host Materials
摘要： 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-(diphenylamino)phenyl)pyridin-2-yl)phenyl)-N-phenylbenzenamine (DTPAPy), are synthesized from modifying the commonly adapted host material 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine (DCzPPy). The HOMO 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 TADF emitter, 9,9-dimethyl-9,10-dihydroacridine-2,4,6-triphenyl-1,3,5-triazine (DAMC-TRZ), 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-butyphenyl) 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 white OLED show the low efficiency roll-off with external quantum efficiencies at the brightness of 1000 cd m-2 (EQE1000) 18.7% and 16.2% respectively, and are the highest performance records among the solution-processed TADF bluish-green and T-P WOLEDs.
关键词： low efficiency roll-off,solution process,bipolar host material,TADF bluish-green organic light-emitting diode,hybrid white organic light emitting diode
更新于2025-09-12 10:27:22
-
Highly efficient TADF OLEDs with low efficiency roll-off based on novel acridine–carbazole hybrid donor-substituted pyrimidine derivatives
摘要： Dimethyl acridine (Ac) and carbazole (Cz) donors are fused to produce acridine–carbazole hybrid donors, 12AcCz (8,8-dimethyl-5-phenyl-8,13-dihydro-5H-indolo[2,3-c]acridine) and 23AcCz (13,13-dimethyl-7-phenyl-7,13-dihydro-5H-indolo[3,2-b]acridine). By combining TPPM (2,4,6-triphenylpyrimidine) acceptor with the Ac–Cz-fused donors of 12AcCz and 23AcCz, two emitters, 12AcCz-PM (13-(4-(2,6-diphenylpyrimidin-4-yl)phenyl)-8,8-dimethyl-5-phenyl-8,13-dihydro-5H-indolo[2,3-c]acridine) and 23AcCz-PM (5-(4-(2,6-diphenylpyrimidin-4-yl)phenyl)-13,13-dimethyl-7-phenyl-7,13-dihydro-5H-indolo[3,2-b]acridine), are designed and synthesized. The impact of the different fused topologies of the hybrid donors on molecular configuration, photophysical and optoelectrical characters are systematically investigated. For 12AcCz-PM, the large steric hindrance between donor and acceptor compels Ac of 12AcCz to be crooked, which endows it with the relatively planar quasi-axial conformation. No blatant TADF character is observed, but the 12AcCz-PM doped device still presents the ultradeep blue emission with CIEx, y of (0.15, 0.05) and maximum external quantum efficiency (EQEmax) of 6.4%. Whereas, 23AcCz-PM shows quasi-equatorial conformation and possesses notable TADF behavior. The 23AcCz-PM doped device reachs the EQEmax of 28.4% at low dopant concentration and 26.1% at high dopant concentration. Additionally, low efficiency roll-off (EQEs of 24.8% at 1000 cd m-2 and 20.7% at 5000 cd m-2) further confirms its superiorities as a TADF emitter.
关键词： novel acridine–carbazole hybrid donors,highly efficient TADF OLEDs,low efficiency roll-off,thermally activated delayed fluorescence
更新于2025-09-11 14:15:04
-
Synthesis and Characteristics of New Organic Red Emissive Material Based on Phenanthro[9,10-d]imidazole
摘要： Red emission is one of the three primary colors that are essential for the realization of full-color displays and solid-state lightings. High solid-state efficiency is a crucial factor for the applications in organic light emitting diodes (OLEDs). In this work, two new donor-acceptor-donor type phenanthro[9,10-d]imidazole (PIM) -based derivatives, (2Z,2'Z)-2,2'-(1,4-phenylene)bis(3-(4-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenyl)acrylonitrile) (PIDSB) and 2,3-bis(4'-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)-[1,1'-biphenyl]-4-yl)fumaronitrile (PIDPh), are designed and synthesized. Both of them possess high thermal stabilities. PIDPh shows typical characteristics of aggregation-induced emission enhancement, while PIDSB displays aggregation-caused quenching effect. They both exhibit much red-shifted emissions compared with PIM owing to intramolecular charge transfer. In film state, the emission peaks of PIDSB and PIDPh locate at 538 nm and 605 nm with high photoluminescent quantum yields of 63.82% and 41.26%, respectively. The non-doped OLED using PIDPh as the active layer shows the maximum external quantum efficiency of 2.06% with a very low efficiency roll-off, and exhibits the electroluminescent peak at 640 nm with a Commission Internationale de l'éclairage coordinate of (0.617,0.396), meeting well with the criteria of red OLEDs.
关键词： red emissive material,high solid-state fluorescent efficiency,OLED,Phenanthro[9,10-d]imidazole,low efficiency roll-off
更新于2025-09-09 09:28:46