Abstract Four single polymers with two kinds of attachment of orange chromophore to blue polymer host for white electroluminescence (EL) were designed. The effect of the side‐chain attachment and main‐chain attachment on the EL efficiencies of the resulting polymers was compared. The side‐chain‐type single polymers are found to exhibit more efficient white EL than that of the main‐chain‐type single polymers. Based on the side‐chain‐type white single polymer with 4‐(4‐alkyloxy‐phenyl)‐7‐(4‐diphenylamino‐phenyl)‐2,1,3‐benzothiadiazoles as the orange‐dopant unit and polyfluorene as the blue polymer host, white EL with simultaneous orange (λ max = 545 nm) and blue emission (λ max = 432 nm/460 nm) is realised. A single‐layer device (indium tin oxide/poly(3,4‐ethylenedioxythiophene)/polymer/Ca/Al) made of these polymers emits white light with the Commission Internationale de l'Éclairage coordinates of (0.30,0.40), possesses a turn‐on voltage of 3.5 V, luminous efficiency of 10.66 cd A –1 , power efficiency of 6.68 lm W –1 , and a maximum brightness of 21 240 cd m –2 .
Abstract New single‐polymer electroluminescent systems containing two individual emission species—polyfluorenes as a blue host and 2,1,3‐benzothiadiazole derivative units as an orange dopant on the main chain—have been designed and synthesized by Wang and co‐workers on p. 957. The resulting single polymers are found to have highly efficient white electroluminescence with simultaneous blue and orange emission from the corresponding emitting species. A single‐layer device has been fabricated that has performance characteristics roughly comparable to those of organic white‐light‐emitting diodes with multilayer device structures. New single‐polymer electroluminescent systems containing two individual emission species—polyfluorenes as a blue host and 2,1,3‐benzothiadiazole derivative units as an orange dopant on the main chain—have been designed and synthesized. The resulting single polymers are found to have highly efficient white electroluminescence with simultaneous blue (λ max = 421 nm/445 nm) and orange emission (λ max = 564 nm) from the corresponding emitting species. The influence of the photoluminescence (PL) efficiencies of both the blue and orange species on the electroluminescence (EL) efficiencies of white polymer light‐emitting diodes (PLEDs) based on the single‐polymer systems has been investigated. The introduction of the highly efficient 4,7‐bis(4‐( N ‐phenyl‐ N ‐(4‐methylphenyl)amino)phenyl)‐2,1,3‐benzothiadiazole unit to the main chain of polyfluorene provides significant improvement in EL efficiency. For a single‐layer device fabricated in air (indium tin oxide/poly(3,4‐ethylenedioxythiophene): poly(styrene sulfonic acid/polymer/Ca/Al), pure‐white electroluminescence with Commission Internationale de l'Eclairage (CIE) coordinates of (0.35,0.32), maximum brightness of 12 300 cd m –2 , luminance efficiency of 7.30 cd A –1 , and power efficiency of 3.34 lm W –1 can be obtained. This device is approximately two times more efficient than that utilizing a single polyfluorene containing 1,8‐naphthalimide moieties, and shows remarkable improvement over the corresponding blend systems in terms of efficiency and color stability. Thermal treatment of the single‐layer device before cathode deposition leads to the further improvement of the device performance, with CIE coordinates of (0.35,0.34), turn‐on voltage of 3.5 V, luminance efficiency of 8.99 cd A –1 , power efficiency of 5.75 lm W –1 , external quantum efficiency of 3.8 %, and maximum brightness of 12 680 cd m –2 . This performance is roughly comparable to that of white organic light‐emitting diodes (WOLEDs) with multilayer device structures and complicated fabrication processes.
Abstract New single‐polymer electroluminescent systems containing two individual emission species—polyfluorenes as a blue host and 2,1,3‐benzothiadiazole derivative units as an orange dopant on the main chain—have been designed and synthesized. The resulting single polymers are found to have highly efficient white electroluminescence with simultaneous blue (λ max = 421 nm/445 nm) and orange emission (λ max = 564 nm) from the corresponding emitting species. The influence of the photoluminescence (PL) efficiencies of both the blue and orange species on the electroluminescence (EL) efficiencies of white polymer light‐emitting diodes (PLEDs) based on the single‐polymer systems has been investigated. The introduction of the highly efficient 4,7‐bis(4‐( N ‐phenyl‐ N ‐(4‐methylphenyl)amino)phenyl)‐2,1,3‐benzothiadiazole unit to the main chain of polyfluorene provides significant improvement in EL efficiency. For a single‐layer device fabricated in air (indium tin oxide/poly(3,4‐ethylenedioxythiophene): poly(styrene sulfonic acid/polymer/Ca/Al), pure‐white electroluminescence with Commission Internationale de l'Eclairage (CIE) coordinates of (0.35,0.32), maximum brightness of 12 300 cd m –2 , luminance efficiency of 7.30 cd A –1 , and power efficiency of 3.34 lm W –1 can be obtained. This device is approximately two times more efficient than that utilizing a single polyfluorene containing 1,8‐naphthalimide moieties, and shows remarkable improvement over the corresponding blend systems in terms of efficiency and color stability. Thermal treatment of the single‐layer device before cathode deposition leads to the further improvement of the device performance, with CIE coordinates of (0.35,0.34), turn‐on voltage of 3.5 V, luminance efficiency of 8.99 cd A –1 , power efficiency of 5.75 lm W –1 , external quantum efficiency of 3.8 %, and maximum brightness of 12 680 cd m –2 . This performance is roughly comparable to that of white organic light‐emitting diodes (WOLEDs) with multilayer device structures and complicated fabrication processes.
Abstract To realize the practical application of carbon dots (CDs), it is crucial to devise straightforward techniques that can finely modulate the fluorescent properties of CDs. Apart from that, it is imperative to weaken the aggregation‐caused quenching (ACQ) effect, which poses a significant challenge to the utilization of solid‐state CDs. In this work, three CDs named as CDs‐1, CDs‐2, and CDs‐3 are synthesized, and the fluorescence tuning of these CDs is successfully realized, assisted by cetyltrimethylammonium bromide (CTAB) surfactant, because its unique molecular structure is conducive in bolstering fluorescence intensity and adjusting emission wavelength. Furthermore, the luminescence of solid‐state CDs is successfully achieved by employing CTAB as substrate in the matrix‐assisted synthesis of composites CDs‐1@CTAB, CDs‐2@CTAB, and CDs‐3@CTAB. Notably, the photoluminescence quantum yield (PLQY) of CDs‐2@CTAB reaches an impressive value as high as 79.31%, surpassing the value of 70.29% obtained by pristine CDs‐2. The experimental results reveal that CDs@CTAB composites exhibit intriguing afterglow characteristics including room temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF). This work confirms the versatility of CDs and highlights the significance of surfactant‐assisted strategies in improving the performance of CDs.
The utilization of lanthanide (Ln) complexes in the realm of organic light-emitting diodes (OLEDs) has garnered extensive interest, particularly in their role as luminescent materials or electron trappers. A series of gadolinium (Gd) complexes with energy levels of high HOMO/LUMO and different triplet state energies were designed and synthesized by introducing substituents with different electronic effects onto the pyrazolone derivative ligands. Subsequently, these complexes were precisely purified by vacuum sublimation and codoped into the light-emitting layer (EML) of the OLEDs. This process was facilitated through the well-matched HOMO/LUMO levels and triplet energies among various functional materials. Consequently, the maximum external quantum efficiencies of blue, red, and green OLEDs were simultaneously enhanced with the ratios of 119%, 28%, and 71%, respectively. This improvement can be credited to the introduction of Gd(III) complex molecules within EMLs, which helps to capture excess holes and improve carriers' balance.
High-efficiency white electroluminescence from a single polymer is achieved by enhancing the electroluminescence efficiency and effecting a red-shift in the emission spectrum of the blue emissive species. A single-layer device of the resultant polymer exhibits a higher luminous efficiency than the nonmodified species (12.8 cd A–1, see figure) and an external quantum efficiency of 5.4 % with CIE coordinates of (0.31,0.36), exemplifying the success of the reported methodology. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2089/2007/c2942_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.
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