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![Chemical structures of the a) dimeric dopant [RuCp*Mes]2 and b) host material (F8BT).](publication/339543904/figure/fig1/AS:11431281173047197@1688746914115/Chemical-structures-of-the-a-dimeric-dopant-RuCpMes2-and-b-host-material-F8BT.png)
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![Chemical structures of the a) dimeric dopant [RuCp*Mes]2 and b) host...](publication/339543904/figure/fig1/AS:11431281173047197@1688746914115/Chemical-structures-of-the-a-dimeric-dopant-RuCpMes2-and-b-host-material-F8BT_Q320.jpg)
n‐Doping electron‐transport layers (ETLs) increases their conductivity and improves electron injection into organic light‐emitting diodes (OLEDs). Because of the low electron affinity and large bandgaps of ETLs used in green and blue OLEDs, n‐doping has been notoriously more difficult for these materials. In this work, n‐doping of the polymer poly[...
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... In view of this improvement in the properties of the F8BT-M device, future optimizations can be carried out based on molar mass and coupling syntheses and/or substitutions in order to transform this copolymer into a polyelectrolyte or a functionalized copolymer [55,91,92] and also use it as an ETL for light-emitting devices. However, the results obtained so far serve as a guide for future work with this material. ...
Fluorene-benzothiadiazole (PFBT), commercially known as F8BT, and fluorene-thiophene (PFT) copolymers were synthesized by the Suzuki-Miyaura coupling polycondensation technique in the presence of a phase transfer catalyst (Aliquat 336). These novel copolymers showed higher molar masses, lower dispersivity, and thermal stability above 400 °C when synthesized under the modified (M) action of Aliquat 336 (F8BT-M). Polymer Light-emitting diodes (PLEDs) were assembled with the novel synthesized copolymers as the emitter layer. For F8BT-M, a maximum luminance of 327 cd/m2 was achieved, while a diode containing just the commercial F8BT resulted in only 210 cd/m2. As for the PFT copolymers, it was observed that for the Aliquat 336 sample synthesized in a 60h extended (E) (PFT-ME), the luminance of the PLED was much higher than that where the reaction time was 48 h (PFT-M), with a luminance of 168 cd/m2 and 54 cd/m2, respectively. Without Aliquat 336, the PFT copolymer did not show an electroluminescent signal. The improved electroluminescence in the copolymers with Aliquat 336 was attributed to the improved synthesis conditions, i.e., reaction time and catalytic system employed. The results suggest that copolymers with luminescent and morphological properties, more suitable for light-emitting devices, might be obtained with simple modifications during synthetic polycondensation reactions.
... [30][31][32][33][34] As an alternative, dimer-type dopant molecules have been proposed to generate more than one charge, but the enlarged size of the incorporated dopant considerably disrupts the CP chain arrangement, thereby deteriorating the carrier transport characteristics of the doped CP films. [35][36][37][38][39][40] On the other hand, improvement of dopant reactivity has been suggested by using transition metals to enhance doping efficiency of n-type organic semiconductors. 41 Novel CPs have also been suggested to directly generate bipolaronic charge carriers via two-electron transfer to F4-TCNQ through double doping. ...
... Therefore, the calculated color gamuts of the pixels were the same for different sheet resistances of the top electrodes, as An OLED comprises many organic layers between the electrodes and has very high resistance. However, in recent years, the conductivity of organic layers in OLED has been increased for low driving voltages by developing novel organic materials and using an n-type and p-type doping method [28][29][30][31] . Therefore, to investigate the effect of the resistance of organic layers, while considering the electrical crosstalk between pixels, we calculated the current crosstalk ratios and color gamut by changing the sheet resistance of the common organic layer from 1 KΩ/□ to 1 TΩ/□, as shown in Fig. 6. ...
Organic light-emitting diode (OLED) microdisplays have received great attention owing to their excellent performance for augmented reality/virtual reality devices applications. However, high pixel density of OLED microdisplay causes electrical crosstalk, resulting in color distortion. This study investigated the current crosstalk ratio and changes in the color gamut caused by electrical crosstalk between sub-pixels in high-resolution full-color OLED microdisplays. A pixel structure of 3147 pixels per inch (PPI) with four sub-pixels and a single-stack white OLED with red, green, and blue color filters were used for the electrical crosstalk simulation. The results showed that the sheet resistance of the top and bottom electrodes of OLEDs rarely affected the electrical crosstalk. However, the current crosstalk ratio increased dramatically and the color gamut decreased as the sheet resistance of the common organic layer decreased. Furthermore, the color gamut of the OLED microdisplay decreased as the pixel density of the panel increased from 200 to 5000 PPI. Additionally, we fabricated a sub-pixel circuit to measure the electrical crosstalk current using a 3147 PPI scale multi-finger-type pixel structure and compared it with the simulation result.
... [17][18][19][20][21][22] Many efforts have devoted to exploiting air-stable n-dopants, which are usually stable at room temperature (RT) while active when heated or under radiation. [23][24][25][26][27][28][29][30][31][32] Among the air-stable n-dopants, benzimidazole (BI) derivatives, especially 1,3-Dimethyl-2-(4-(dimethylamino)phenyl)-2,4-dihydro-1H-benzimidazole, N-DMBI-H (see Fig. 1 and Fig. S1), is believed to be the most popular and successful one owing to its good stability and solution processability. 17,33 It has been applied to dope broad types of semiconductors including inorganics and organics. ...
Precursor dopants have been extensively applied for n-doping of organic semiconductors (OSCs) to address the trade-off between dopant reducibility and stability. N-DMBI-H derivates are believed as one of the most successful air-stable n-dopants. Two doping mechanisms, i.e., hydrogen atom transfer (HAT) and hydride transfer (HYT), have been suggested but the dominance of them remains controversial. In this work, we rationalize the thermodynamics and kinetics of HAT and HYT reactions between N-DMBI-H derivates and a variety of OSCs and conjugated polymers based on the density functional theory, and manifest that the HYT via concerted electron and hydrogen atom transfer is the most viable doping mechanism. We find two linear relations between the free energy change of HYT, \Delta G_HYT, and the electron affinity (EA) of OSCs as well as the ionization energy (IE) of dopant radicals, D, and the Brnsted-Evans-Polanyi relation between the \Delta G_HYT and the activation barrier of HYT, \Delta G^≠. By correlating important thermodynamic and kinetic parameters of HYT to facile properties of OSCs and dopants, molecular descriptors of n-doping are uncovered. Furthermore, an EA(OSC) - IE(D) > 1.0 eV criterion is proposed for achieving a high doping efficiency based on the requirement \Delta G_HYT < 0. Finally, new quinoid-structure polymers with EA > 4.0 eV and good backbone planarity are designed as potential n-type OSCs. The molecular descriptors and criterion discovered provide a simple and operable way to speed up the development of n-type OSCs and dopants by high-throughput screening and machine learning technique
... 63 There are a number of different classes of soluble n-dopants including benzimidazoles, 64-67 amines, 68,69 carbenes, 70,71 and phosphines 69,72 which could be considered for TEGs. Some of the most widely studied and commercially available high performing n-type dopants include [73][74][75] and 1,5,7-triazabicyclo [4.4.0] dec-5-ene (TBD). 76,77 Other n-dopants, such as triaminomethane (TAM) 68,78 and 1,3-dimethylimidazolium-2-carboxylate (DMImC), 70,78 have a smaller molecular volume and improved miscibility with the host, but these are not commercially available at high purities. ...
Organic thermoelectric generators (TEGs) are a prospective class of versatile energy-harvesters that can enable the capture of low-grade heat and provide power to the growing number of microelectronic devices and sensors in the Internet of Things. The abundance, low-toxicity, and tunability of organic conducting materials along with the scalability of the fabrication techniques promise to culminate in a safe, low-cost, and adaptable device template for a wide range of applications. Despite recent breakthroughs, it is generally recognized that significant advances in n-type organic thermoelectric materials must be made before organic TEGs can make a real impact. Yet, in this perspective, we make the argument that to accelerate progress in the field of organic TEGs, future research should focus more effort into the design and fabrication of application-oriented devices, even though materials have considerable room for improvement. We provide an overview of the best solution-processable organic thermoelectric materials, design considerations, and fabrication techniques relevant for application-oriented TEGs, followed by our perspective on the insight that can be gained by pushing forward with device-level research despite suboptimal materials.
... The conductivity of undoped and CN6-CP-doped POPy 2 was measured in UHV using an interdigitated electrode platform deposited on quartz, with a setup described elsewhere 35 (details are given in the Experimental Section). Note that the conductivity of POPy 2 doped with (RuCp*Mes) 2 has been previously characterized. ...
... Monolayer Doping, also known in the literature as Molecular Doping (MD), has been demonstrated as a low-cost alternative to conventional doping techniques [1,2]. Differently from another literature process, where guest molecules-working as charge transfer layer-are put in contact with the host material [3][4][5][6][7], the method involves the deposition of dopant-containing molecules from the liquid phase, called precursors, and the subsequent drive-in of the dopant atoms by thermal annealing. MD can provide nand p-type doping and is capable of a good range of carrier doses and diffusion depths, obtained by controlling the precursor chemical characteristics, the deposition conditions, and the thermal budget [1,2,[8][9][10][11][12][13]. ...
Molecular Doping (MD) involves the deposition of molecules, containing the dopant atoms and dissolved in liquid solutions, over the surface of a semiconductor before the drive-in step. The control on the characteristics of the final doped samples resides on the in-depth study of the molecule behaviour once deposited. It is already known that the molecules form a self-assembled monolayer over the surface of the sample, but little is known about the role and behaviour of possible multiple layers that could be deposited on it after extended deposition times. In this work, we investigate the molecular surface coverage over time of diethyl-propyl phosphonate on silicon, by employing high-resolution morphological and electrical characterization, and examine the effects of the post-deposition surface treatments on it. We present these data together with density functional theory simulations of the molecules–substrate system and electrical measurements of the doped samples. The results allow us to recognise a difference in the bonding types involved in the formation of the molecular layers and how these influence the final doping profile of the samples. This will improve the control on the electrical properties of MD-based devices, allowing for a finer tuning of their performance.
... Conductive polymers have a backbone that is π-conjugated (alternating single and double bonds), allowing overlapping of bound electrons in the polymeric chain [24]. Through incorporating various electron releasing/withdrawing functional groups into the polymeric backbone and managing the electron-hole injecting/ transporting ability of the synthesized conducting polymer, and the conductivity of the polymers can be effectively tuned to achieve emission in the desired luminance range [25]. The creation of charge carriers induces an increase in conductivity. ...
Many changes have arisen in the world of display technologies as time has passed. In the vast area of display technology, Organic light-emitting diode is a recent and exciting discovery. Organic light-emitting diodes (OLEDs) have received a lot of curiosity among the researcher in recent years as the next generation of lighting and displays due to their numerous advantages, such as superior efficiency, mechanical flexibility and stability, chemical versatility, ease of fabrication, and so on. It works on the theory of electroluminescence, which is a mechanism in which electrical energy converts to light energy. Organic LEDs have a thickness of 100 to 500 nanometers or 200 times that of human hair. In OLEDs, organic material can be used in two or three layers. The emissive layer plays a key role in OLEDs. Polymers are used in the emissive layer to enhance the efficiency of OLEDs at the same time self-luminescence materials are used in OLEDs. In displays, this self-illuminating property removes the need for backlighting. Compared to LEDs and LCDs, OLED displays are smaller, lighter, and more portable.
... Nonetheless, the doping process, especially the n-doping one in pin-structure OLEDs, is quite sophisticated, and a specially designed fabrication facility is needed. Because the hole mobility is typically two magnitudes higher than electron mobility for typical transporting materials for OLEDs, simply increasing the electron mobility of the ETL could decrease the device driving voltage and broaden the ERZ, leading to an improved LT of corresponding OLEDs [29,30]. For instance, KBH4 was doped in ETL of an inverted bottom emission OLED as an n-dopant to increase electron injection and reduced the turn-on voltage from 10.1 to 3.0 V [29]. ...
... An OLED with n-doped ETL consisting of poly((9,9-dioctylfluorene-2,7-diyl)-alt-(benzo(1-3)thiadiazol-4,7-diyl)) and (pentamethylcyclopentadienyl) (1,3,5-trimethylbenzene)ruthenium dimer was reported recently. The conductivity and luminance of this device have been improved by three and four orders of magnitude when compared to the device with a non-doped ETL [30]. ...
The efficiency roll-off and operational lifetime of organic light-emitting diodes (OLEDs) with a tetradentate Pt(II) emitter is improved by engaging an n-doped electron-transporting layer (ETL). Compared to those devices with non-doped ETL, the driving voltage is lowered, the charged carrier is balanced, and the exciton density in the emissive layer (EML) is decreased in the device with n-doped ETL with 8-hydroxyquinolinolatolithium (Liq). High luminance of almost 70,000 cd m−2 and high current efficiency of 40.5 cd A−1 at high luminance of 10,000 cd m−2 is achieved in the device with 50 wt%-Liq-doped ETL. More importantly, the extended operational lifetime of 1945 h is recorded at the initial luminance of 1000 cd m−2 in the 50 wt%-Liq-doped device, which is longer than that of the device with non-doped ETL by almost 10 times. This result manifests the potential application of tetradentate Pt(II) complexes in the OLED industry.
