Search

A new family of symmetrical fluorene derivatives with different types of substituents attached to the C-2 and C-7 positions of the fluorene core synthesized by the Sonogashira coupling reactions is reported. The electronic structures and the properties of the compounds investigated by means of photoelectron emission spectroscopy, UV–Vis absorption and photoluminescent spectroscopy as well as by DFT and TD-DFT theoretical calculations are discussed. It is shown that the nature of substituents influences the π-conjugation of the molecules. No intermolecular charge transfer within the investigated wavelength range is observed. The applicability of the synthesized compounds in organic light-emitting diodes (OLEDs) based on exciplex emission is demonstrated. The advanced co-deposition technique with the tuned OLED architecture was applied and resulted in improved OLED parameters. [ABSTRACT FROM AUTHOR]

Stable and efficient deep‐blue organic light‐emitting diodes (OLEDs) are in high demand for display and lighting applications but are rarely reported due to their poor operational lifetimes. Herein, the study designs and synthesizes two novel N‐heterocyclic carbene (NHC)‐based tetradentate Pt(II) complexes PtON5‐dtb and PtON5N‐dtb, and thoroughly investigate their electrochemical and photophysical properties. Functionalization of the NHC moieties can increase the metal‐to‐ligand charge transfer (1/3MLCT) characters in their lowest triplet excited‐states, resulting in significantly shortened photoluminescent lifetimes and remarkably improved device performance. A deep blue OLED employing PtON5N‐dtb as an emitter exhibits a narrow spectral bandwidth with a full‐width at half maximum (FWHM) of 30 nm and a CIEy value of 0.17 and demonstrates a maximum external quantum efficiency (EQE) of 20.4% with a small efficiency roll‐off, which maintains a high EQE of 18.5% at 1000 cd m−2. Moreover, the deep blue OLED also realizes a long‐measured operational lifetime LT90 (time to 90% of the initial luminance) of 71 hours with an initial brightness of 1134 cd m−2, corresponding to an estimated device lifetime LT90 of 85 h at 1000 cd m−2. This represented an eightfold lifetime improvement for PtON5N‐dtb‐based deep blue OLED compared to PtON7‐dtb in the same device setting. [ABSTRACT FROM AUTHOR]

Two isomeric homoleptic Ir(III) complexes with pyridinopyridazine derivative ligands were prepared first. Due to its stronger intramolecular hydrogen bonding and intermolecular interactions, complex IrPPM has a higher decomposition temperature (5% weight loss) of 387°C than IrPPP (354°C). They have similar UV–Vis absorption and photoluminescence spectra in CH2Cl2 solution with photoluminescence peaks around 635–636 nm. However, the emission peak of IrPPM in neat powder obviously red‐shifted to 652 nm, and that of IrPPP blue‐shifted to 626 nm. Simultaneously, complex IrPPM has a lower photoluminescence quantum yield of 0.3 than IrPPP (0.5). Efficient saturated red OLED devices are developed with Commission Internationale de L'Eclairage color coordinates of (0.67, 0.32) and (0.66, 0.32), respectively. The maximum external quantum efficiencies of both devices exceed 11%. These results demonstrate the great potential of pyridinopyridazine derivatives for developing new iridium complexes for OLED applications. [ABSTRACT FROM AUTHOR]

Three new Pb(II) complexes of 3‐(2‐pyridyl)‐5‐(4‐methoxyphenyl)‐1,2,4‐triazine (PMPT) ligand with different anionic co‐ligands (1: nitrate, 2: perchlorate and 3: isothiocyanate) in 2 : 1 molar ratios of PMPT ligands and lead(II) salts, [Pb(PMPT)2(NO3)2] (1), [Pb(PMPT)2(ClO4)2] (2) and [Pb(PMPT)2(NCS)2] (3) were synthesized and characterized by physicochemical (CHN, FT‐IR and 1H NMR) and single‐crystal X‐ray diffraction methods. By considering the obtained structural parameters, the lead atoms in 1, 2 and 3 have PbN4O4, PbN4O2 and PbN6 environments, respectively, with holodirected (for 1) and hemidirected (for 2 and 3) coordination spheres. We used electro‐optical Pb(II) complexes family as emitting layer to investigate in fabrication of OLEDs. The current–voltage, luminescence‐voltage characteristics and the absorption (Abs) and electroluminescence (EL) properties of the complex have been investigated. The forester radius, quantum yield, and electroluminescence have been studied. [ABSTRACT FROM AUTHOR]

Deep‐blue multi‐resonance (MR) emitters with stable and narrow full‐width‐at‐half‐maximum (FWHM) are of great importance for widening the color gamut of organic light‐emitting diodes (OLEDs). However, most planar MR emitters are vulnerable to intermolecular interactions from both the host and guest, causing spectral broadening and exciton quenching in thin films. Their emission in the solid state is environmentally sensitive, and the color purity is often inferior to that in solutions. Herein, a molecular design strategy is presented that simultaneously narrows the FWHM and suppresses intermolecular interactions by combining intramolecular locking and peripheral shielding within a carbonyl/nitrogen‐based MR core. Intramolecularly locking carbonyl/nitrogen‐based bears narrower emission of 2,10‐dimethyl‐12,12‐diphenyl‐4H‐benzo[9,1]quinolizino[3,4,5,6,7‐defg]acridine‐4,8(12H)‐dione in solution and further with peripheral‐shielding groups, deep‐blue emitter (12,12‐diphenyl‐2,10‐bis(9‐phenyl‐9H‐fluoren‐9‐yl)−4H‐benzo[9,1]quinolizino[3,4,5,6,7‐defg]acridine‐4,8(12H)‐dione, DPQAO‐F) exhibits ultra‐pure emission with narrow FWHM (c.a., 24 nm) with minimal variations (∆FWHM ≤ 3 nm) from solution to thin films over a wide doping range. An OLED based on DPQAO‐F presents a maximum external quantum efficiency (EQEmax) of 19.9% and color index of (0.134, 0.118). Furthermore, the hyper‐device of DPQAO‐F exhibits a record‐high EQEmax of 32.7% in the deep‐blue region, representing the first example of carbonyl/nitrogen‐based OLED that can concurrently achieve narrow bandwidth in the deep‐blue region and a high electroluminescent efficiency surpassing 30%. [ABSTRACT FROM AUTHOR]

Three novel conjugated molecules have been synthesized: 2‐(fluoranthen‐3‐yliminomethyl)‐3,4‐ethylenedioxythio‐phene (EIF), 2‐(fluoranthen‐3‐yliminomethyl) thiophene (TIF), and 2‐(fluoranthen‐3‐yliminomethyl) fluorene (FIF). Optical properties were obtained from electronic absorption and emission spectra in DMSO solution. The solvatochromic properties of the molecules have been studied in different solvents. Electrochemical properties were studied by cyclic voltammetry in a Bu4NBF4 (0.1 M)/MeCN organic solution. As part of investigations to explain the nature of electronic transition process, we have performed geometry optimization of both the ground and the vertical excitation states, using the DFT B3LYP/6‐311G (d, p) and TD‐DFT (CPCM)/B3LYP/6‐311G (d, p) approaches, respectively. Theoretical calculations closely match the experimental findings. Results show that EIF, TIF and FIF are potential candidates to be used as electron transport layer in Organic Light‐Emitting Diodes (OLEDs). [ABSTRACT FROM AUTHOR]

In the last past twenty years, research on luminescent platinum (II) complexes has been intensively developed for useful application such as organic light emitting diodes (OLEDs). More recently, new photoluminescent complexes based on diazine ligands (pyrimidine, pyrazine, pyridazine, quinazoline and quinoxaline) have been developed in this context. This review will summarize the photophysical properties of most of the phosphorescent diazine Pt(II) complexes described in the literature and compare the results to pyridine analogues whenever possible. Based on the emission color, and the photoluminescence quantum yield (PLQY) values, the relationship between structure modification, and photophysical properties are highlighted. Tuning of emission color, quantum yields in solution and solid state and, for some complexes, aggregation induced emission (AIE) or thermally activated delayed fluorescence (TADF) properties are described. When emitting OLEDs have been built from diazine Pt(II) complexes, the external quantum efficiency (EQE) values and luminance for different emission wavelengths and in some cases, chromaticity coordinates obtained from devices, are given. Finally, this review highlights the growing interest in studies of new luminescent diazine Pt(II) complexes for OLED applications. [ABSTRACT FROM AUTHOR]

In this study, we present the synthesis of benzimidazo[1,2-a] quinoline-based heterocycles bearing organosulfur and organoselenium moieties through transition-metal-free cascade reactions involving a sequential intermolecular aromatic nucleophilic substitution (SNAr). Both sulfur and selenium derivatives presented absorption maxima located around 355 nm related to spin and symmetry allowing electronic 1π-π* transitions, and fluorescence emission at the violet-blue region (~440 nm) with relatively large Stokes shift. The fluorescence quantum yields were slightly influenced by the chalcogen, with the sulfur derivatives presenting higher values than the selenium analogs. In this sense, the quantum yields for selenium derivatives can probably be affected by the intersystem crossing or even the photoinduced electron transfer process (PET). The compounds were successfully applied in all-solution-processed organic light-emitting diodes (OLEDs), where poly(9-vinylcarbazole) was employed as a dispersive matrix generating single-layer device cells. The obtained electroluminescence spectra are a sum of benzimidazo[1,2-a]quinolines and PVK singlet and/or triplet emissive states, according to their respective energy band gaps. The best diode rendered a luminance of 25.4 cd⋅m−2 with CIE (0.17, 0.14) and current efficiency of 20.2 mcd⋅A−1, a fivefold improvement in comparison to the PVK device that was explained by a 50-fold increase of charge-carriers electrical mobility. [ABSTRACT FROM AUTHOR]

We present a novel pixel design called TurboLED® for reducing display power consumption, as well as extending display lifetime and expanding color gamut. In a TurboLED® display, each pixel comprises stacked LEDs, with independent lighter and deeper red, green and blue emissive units. We demonstrate 48.0% power savings for a TurboLED® display with Rec. 2020 color gamut compared to an OLED display with a standard RGB pixel design. This substantial power savings can extend the daily battery life of smartphones, tablets, laptops and other portable electronic devices by several hours each day. [ABSTRACT FROM AUTHOR]

Third-generation organic light-emitting diodes (OLEDs) based on metal-free thermally activated delayed fluorescent (TADF) materials have sparked tremendous interest in the last decade due to their nearly 100% exciton utilization efficiency, which can address the low-efficiency issue of the first-generation fluorescent emitters and the high-cost issue of the second-generation organometallic phosphorescent emitters. Construction of efficient and stable TADF-OLEDs requires utilizing TADF materials with a narrow singlet–triplet energy gap (ΔEST), high photoluminescence quantum yield (PLQY) and short TADF lifetime. A small ΔEST is necessary for an efficient reverse intersystem crossing (RISC) process, which can be achieved through the effective spatial separation of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). TADF emitters have been generally designed as intramolecular charge transfer (ICT) molecules with highly twisted donor–acceptor (D–A) molecular architectures. A wide variety of combinations of electron donors and acceptors have been explored. In this review, we shall focus on recent progress in organic TADF molecules incorporating strong electron-donor phenoxazine moiety and their application as emitting layer (EML) in OLEDs. [ABSTRACT FROM AUTHOR]

Three new neutral and ionic phosphorescent iridium(III) complexes were successfully prepared using 1‐(6‐methoxynaphthalen‐2‐yl)isoquinoline as the main ligand, while the auxiliary ligand was 2‐(2‐1H‐imidazolyl)pyridine. Three complexes (Ir1, Ir2, Ir3) showed red emission, peaking at 610, 609, and 615 nm, respectively, and they exhibited good solubility and excellent photophysical properties in different solvents, which is suitable to prepare organic light‐emitting diodes (OLEDs) by solution method. Among the three OLEDs prepared by iridium(III) complexes using the solution method, the device based on Ir2 possessed better electroluminescent properties, and its maximum brightness, current efficiency (CE), power efficiency (PE), and the maximum external quantum efficiency (EQE) were 507.2 cd m−2, 0.14 cd A−1, 0.06 lm W−1, and 0.14%. respectively, proving that the three complexes have a certain of potential for OLEDs applications and are expected to expand the applications of iridium(III) complexes for OLEDs. [ABSTRACT FROM AUTHOR]

In this paper, we proposed a novel stacked OLED device, which consists of a single layer of RGB units stacked vertically together. In the stacked OLED display, the pixel aperture ratio is about triple of traditional displays. The color gamut with DCI‐P3 (CIE1931) of the stacked device reaches 99% without color filter. In addition, we explored a pixel circuit suitable for the device, which theoretically improves the lifetime of the device by about 300% in this drive mode. [ABSTRACT FROM AUTHOR]

Investigated nano‐pillar‐based light extraction methods for OLEDs. Explored photosensitive photopolymer (SU‐8) based random nanostructure's impact on light extraction efficiency. Achieved 85% visible spectrum transmittance, highest efficiency with minimal unetched structure thickness. Compared to OLEDs lacking nano‐pillar structure, saw up to 38% improved quantum efficiency and 40% enhanced power efficiency. Insights aid in optimizing these structures for OLED advancement. [ABSTRACT FROM AUTHOR]

The advantages of utilizing dual emission display in relation to information interaction and customized display have been widely acknowledged. Organic light‐emitting devices (OLEDs) are an effective solution for future dual emission displays, however, the influence of electrode materials and device structure results in significant differences in the optical performance on both sides. Here, we adjust the optical microcavity effect to balance the light output from both sides so that the top and bottom of the display can be seen with the same brightness and chromaticity. The structure of an OLED for dual emission display has been fabricated. [ABSTRACT FROM AUTHOR]

To enhance the performance of inkjet OLED/QLED devices, achieving a uniform film during the drying process is crucial. This study aims to improve both intra‐pixel and inter‐pixel uniformity in the drying process of inkjet printing technology. We conducted a comprehensive analysis of drying characteristics under various mixed solvent boiling points in nitrogen(N2) conditions. Additionally, during vacuum drying process, we carefully studied the characteristics based on adjustments in vacuum pressure and heating. Our focus was on analyzing the thickness profiles of dried pixel arrays in different positions: top, center, bottom, and left parts. Through the optimization of vacuum drying using solvents with a high boiling point (BP), we successfully achieved uniform film formation within and between pixels in inkjet‐printed pixel arrays. [ABSTRACT FROM AUTHOR]

Recently, boron (B)/nitrogen (N)‐embedded polycyclic aromatic hydrocarbons (PAHs), characterized by multiple resonances (MR), have attracted significant attention owing to their remarkable features of efficient narrowband emissions with small full width at half maxima (FWHMs). However, developing ultra‐narrowband pure‐green emitters that comply with the Broadcast Service Television 2020 (BT2020) standard remains challenging. Precise regulation of the MR distribution regions allows simultaneously achieving the emission maximum, FWHM value, and spectral shape that satisfy the BT2020 standard. The proof‐of‐concept molecule TPABO‐DICz exhibited ultrapure green emission with a dominant peak at 515 nm, an extremely small FWHM of 17 nm, and Commission Internationale de l′Eclairage (CIE) coordinates of (0.17, 0.76). The corresponding bottom‐emitting organic light‐emitting diode (OLED) exhibited a remarkably high CIEy value (0.74) and maximum external quantum efficiency (25.8 %). Notably, the top‐emitting OLED achieved nearly BT2020 green color (CIE: 0.14, 0.79) and exhibited a state‐of‐the‐art maximum current efficiency of 226.4 cd A−1, thus fully confirming the effectiveness of the above strategy. [ABSTRACT FROM AUTHOR]

Recently, boron (B)/nitrogen (N)‐embedded polycyclic aromatic hydrocarbons (PAHs), characterized by multiple resonances (MR), have attracted significant attention owing to their remarkable features of efficient narrowband emissions with small full width at half maxima (FWHMs). However, developing ultra‐narrowband pure‐green emitters that comply with the Broadcast Service Television 2020 (BT2020) standard remains challenging. Precise regulation of the MR distribution regions allows simultaneously achieving the emission maximum, FWHM value, and spectral shape that satisfy the BT2020 standard. The proof‐of‐concept molecule TPABO‐DICz exhibited ultrapure green emission with a dominant peak at 515 nm, an extremely small FWHM of 17 nm, and Commission Internationale de l′Eclairage (CIE) coordinates of (0.17, 0.76). The corresponding bottom‐emitting organic light‐emitting diode (OLED) exhibited a remarkably high CIEy value (0.74) and maximum external quantum efficiency (25.8 %). Notably, the top‐emitting OLED achieved nearly BT2020 green color (CIE: 0.14, 0.79) and exhibited a state‐of‐the‐art maximum current efficiency of 226.4 cd A−1, thus fully confirming the effectiveness of the above strategy. [ABSTRACT FROM AUTHOR]

This research focuses on a theoretical study of diphenylsulfone-based emitters for thermally activated delayed fluorescence (TADF). The acceptor moiety employed in this study is sulfonyldibenzene, while the donor moiety is 9H-carbazole. The effects of methoxy, thiophene, pyridine, and pyrazine adding on the donor moiety were investigated, resulting in the design of six distinct molecules. Density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods, utilizing the B3LYP functional with 6-311G(d,p) basis sets, were used to assess the properties of these compounds in their singlet, doublet, and triplet states. The calculations encompassed various aspects, including ground state molecular geometry, electronic properties, dipole moments, polarizabilities, frontier orbital energies, density of states, UV-Vis spectra, and IR spectra. The investigation revealed that adding the donor moiety with rings, particularly thiophene and pyridine, resulted in improved properties, including molecular geometry. Furthermore, increasing the D-A dihedral angle was found to increase the energy gap, optical gap, dipole moments, and polarizabilities, while reducing the ∆EST and the overlap between the HOMO and LUMO. Hole-electron analysis demonstrated that all the compounds exhibited localized excitation characteristics, with the electrons being photoinduced locally. These compounds exhibited strong blue emissions, with maximum wavelengths ranging from 387.462 to 458.286 nm in the singlet-triplet states. Moreover, the designed compounds exhibited coverage of the entire visible region in their UV-Vis spectra when in the doublet state. Based on these findings, these compounds show promise as TADF emitters in organic light-emitting diodes (OLEDs), providing improvements in efficiency and properties. [ABSTRACT FROM AUTHOR]

The fabrication of optoelectronic devices using low‐cost inkjet printing techniques is a topic of great interest to the scientific and industrial community and represents a step toward the full deployment of solution‐processable organic light emitting diodes (OLEDs), particularly for commercial lighting and signaling applications. Herein, the inkjet printing of tBuCzDBA (9,10‐bis(4‐(3,6‐di‐tert‐butyl‐9H‐carbazol‐9‐yl)−2,6‐dimethylphenyl)−9,10‐diboraanthracene) is reported, a high‐performing thermally activated delayed fluorescence (TADF) emitter for OLEDs. Optimizing the surface tension values of the ink formulations and the associated wetting behavior are crucial parameters for achieving a uniform and homogeneous printed thin film. In particular, it is observed that using a proper mixture of solvents with different surface tensions, it is possible to generate Marangoni flows inside the drop, which triggers a very fast drying process, ensuring optimized morphological and optical properties in the inkjet printed tBuCzDBA‐based film. OLEDs exploiting this film as an emissive layer are then fabricated, achieving a maximum luminance of 32 000 cd m−2, a current efficiency of 27.5 cd A−1, and an external quantum efficiencyof 10%. To the best of the knowledge, this is the highest efficiency reported to date for self‐hosted TADF inkjet‐printed OLEDs. [ABSTRACT FROM AUTHOR]

This study proposes a novel approach to develop highly efficient, narrow‐emitting violet materials based on boron and oxygen polycyclic aromatic hydrocarbon multiple resonance structure. Herein, B‐2OCz is developed by fusing indole with a 5,9‐dioxa‐13bboranaphtho[3,2,1‐de]anthracene (DOBNA) core to enhance its thermally activated delayed fluorescence (TADF) properties and molecular rigidity. On the other hand, the B‐2OCz‐Si is decorated with a bulky tetraphenylsilyl substituent. B‐2OCz‐Si exhibits exceptional features such as violet emission at 397 nm, a very small full width at half maximum of 16 nm, and 82% of photoluminescence quantum yield. The B‐2OCz‐Si devices achieve a high external quantum efficiency of over 15%, violet emission with a peak wavelength of 423 nm, and color coordinates of (0.156, 0.037). Furthermore, the B‐2OCz‐Si is used as an electron transport type host material for phosphorescent organic light‐emitting diodes (PhOLEDs), based on its high triplet energy and TADF properties. As compared to the conventional triazine based host materials, these newly developed DOBNA‐based materials display superior device lifetime performance. All these potential aspects corroborate that this new class of DOBNA‐based materials can work as a promising host material for PhOLEDs and violet‐emitting fluorescent devices. [ABSTRACT FROM AUTHOR]

In general, a large donor‐acceptor dihedral angle is required to guarantee sufficient frontier molecular orbitals separation for thermally activated delayed fluorescence (TADF) emitters, which is intrinsically unfavorable for the radiative transition. We present a molecular design method favoring both reverse intersystem crossing (RISC) and radiative transitions even at a moderate D−A angle. A blue TADF emitter TrzBuCz‐CN was designed with triazine/tert‐butylcarbazole as donor/acceptor and cyano (CN) incorporated on the phenylene bridge. In comparison with the methyl decoration in similar way (TrzBuCz−Me), CN decoration reduced the D−A dihedral angle from 70° to 60°, which is intrinsically not favorable for sufficient FMO separation, but unexpectedly reduced the singlet and triplet energy gap (ΔEST) and thus facilitated TADF feature by pulling down the lowest singlet state energy. While the reduced distorsion instead improved the HOMO‐LUMO overlap and boosted the fluorescence quantum yield from 41 % to 94 %. The blue organic light‐emitting diode of TrzBuCz‐CN exhibited an external quantum efficiency of 13.7 % with emission peak at 466 nm, greatly superior to 6.0 % of TrzBuCz−Me. The result provides a feasible design strategy to facilitate both RISC and radiation processes by CN decoration of the linking bridge of TADF emitters. [ABSTRACT FROM AUTHOR]

Multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters can enable narrowband emission with high color purity and electroluminescence efficiency. Nitrogen/carbonyl (N/C=O) system is receiving increasing attention while the nitrogen/ boron (N/B) system has been widely studied. Donor decoration is an effective approach for N/B type MR-TADF system but always leads to broadening and red-shifting of the emission band in N/C=O MR-TADF system. We attribute these unfavorable phenomena to the formation of intramolecular charge transfer between the MR-core and peripheral donors. To address this issue, we have developed a new strategy by decorating DMQAO (a fused N/C=O MR-core) with a triazine acceptor and a neutral terphenyl group to construct MTDMQAO and MBDMQAO, respectively. The introduction of the triazine acceptor not only realizes efficient narrowband emission in MTDMQAO, but also accelerates the reverse intersystem crossing process through enhanced spin-orbital coupling. As a result, MTDMQAO exhibits a significantly higher external quantum efficiency of 29.4% compared to the referent emitters, validating the rationality of our derivation strategy. This study highlights the potential of the N/C=O system for MR-TADF emitters and provides important insights for understanding the difference between N/B and N/C=O systems. [ABSTRACT FROM AUTHOR]

The review is devoted to analysis of photo- and electroluminescent properties of metal complexes (Al, Be, Mg, Ga, In, Zn, and B) based on substituted quinoline derivatives. Literature data shows that changing the substituents in quinoline ligands and the metal complexing agent can affect the color and intensity of photoluminescence in the corresponding metal complexes. OLED devices fabricated based on these complexes have exhibited high brightness and efficient electroluminescence across a broad spectral range from red to blue. Furthermore, these compounds possess excellent electron-transport properties, enabling their utilization as conductive layers in OLEDs. [ABSTRACT FROM AUTHOR]

A series of green organic light-emitting diodes (OLEDs) that consisted of a tris-(8-hydroxyquinoline)aluminum emitting layer and an N,N′-bis-(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) hole transport layer were fabricated and characterized. The NPB layers were formed using a solution process and heated at different temperatures. All the fabricated OLEDs showed similar electroluminescence spectra: however, different heat treatment temperatures resulted in efficiency variations. The peak luminous efficiency revealed a significant increase by ~70% when the temperature was increased from 80°C to 100°C and a dramatic decrease by ~57% after a further increase in temperature to 110°C. As a result, the best performance was observed from the device with a treatment temperature of 100°C; the maximum luminance and luminous efficiency were 7600 cd/m2 and 2.75 cd/A, respectively. [ABSTRACT FROM AUTHOR]

Color conversion media (CCM) are crucial for realizing cost‐effective, high‐resolution micro‐LED and OLED displays. In this work, we developed green and red organic‐perovskite bilayer CCM that combine the PLQY and color purity of perovskite quantum dots (PeQDs) and the strong blue absorption of perylene‐based organic emitters. The bilayer with thickness of 300 nm showed over 99% blue absorption and PLQY of 77% and 61% for green and red CCM, respectively. [ABSTRACT FROM AUTHOR]

In this paper, we proposed a novel stacked OLED device, which consists of a single layer of RGB units stacked vertically together. In the stacked OLED display, each pixel comprises only one unit OLED, with independent red, green and blue emissive units. Meanwhile, the pixel aperture ratio is about triple of traditional displays. The color gamut with DCI‐P3 (CIE1931) of the stacked device reaches 99% without color filter. In addition, we explored a pixel circuit suitable for the device, which theoretically improves the lifetime of the device by about 300% in this drive mode. [ABSTRACT FROM AUTHOR]

Over the past decade, thermally activated delayed fluorescence (TADF) emitters have garnered tremendous impetus because of their ability to harvest 100% excitons for the light emission in organic light emitting diodes (OLEDs). However, despite their superior external quantum efficiencies (> 35%), the broad emission spectra with associated full‐width‐at‐half maximum (FWHM > 70 nm) present a limiting factor that must be solved. Recently, multiple‐resonance TADF (MR‐TADF) materials based on the heteroatom doped polyaromatic hydrocarbons have gained astonishing attention owing to their remarkable narrowband emission (FWHM < 30 nm). However, emission of the majority of reported MR‐TADF emitters falls in the blue/green region, which inevitably jeopardizes their application in full‐color OLEDs. Therefore, there is an urgent need to develop the new molecular designs for expanding the color‐gamut of MR‐TADF emitters, i.e., λem > 550 nm without compromising the narrowband emission. To the best of current knowledge, no detailed reviews focusing on the different design strategies for producing long‐wavelength (> 550 nm) MR‐TADF emitters have been reported to date. To this end, a review highlighting the recent design advances for constructing long‐wavelength MR‐TADF emitters is presented, and their photophysics and OLED performance is discussed. Finally, the current status and future prospects of long‐wavelength MR‐TADF materials are discussed. [ABSTRACT FROM AUTHOR]

We synthesized zinc oxide nanoparticles (ZnO NPs) by meticulously controlling both temperature and reaction times, allowing us to fine-tune their crystalline properties, morphology, and particle dimensions. This analysis confirmed the existence of a mixture of rod and sphere shapes (ZnO-I), including rod-shaped NPs with an average size of 14.8 nm × 5.2 nm and spherical NPs with an average diameter of 5.27 nm. We subsequently incorporated these synthesized ZnO NPs into organic light-emitting diode (OLED) devices for red, green, and blue colors, utilizing them as the electron injection layer through a solution-based process. The green OLED device using ZnO-I exhibited a promising current efficiency of 4.02 cd/A and an external quantum efficiency of 1.47%. [ABSTRACT FROM AUTHOR]

The use of conjugated polyelectrolytes (CPEs) as interfacial layers (ILs) to increase the efficiency of organic light‐emitting diodes (OLEDs), organic solar cells (OSCs), and organic transistors is a well‐established strategy. Here, the rational process is reported that led to develop the bifunctional poly[(2,7‐(9,9'‐bis(6'‐diethoxylphosphorylhexyl)‐fluorene)‐alt‐(2,7‐(9,9′‐bis(6″‐trimethylammonium bromide)hexyl)‐fluorene)] (PF‐NBr‐EP). PF‐NBr‐EP is successfully incorporated as a cathode IL (CIL) in diverse electronic and optoelectronic devices. The properties of two fluorene‐based CPEs containing, respectively, phosphonate (EP) and ammonium (NBr) moieties used as building blocks for the synthesis of the PF‐NBr‐EP copolymer and their mixtures are investigated to evaluate the combined effect of the two moieties and therefore to gain insight into the behavior of PF‐NBr‐EP chemical structure in the devices. Additionally, the performance of OLEDs and OSCs is analyzed based on established active layers, incorporating all these neat and mixed CILs. [ABSTRACT FROM AUTHOR]

In this paper, several Ir (III) complexes with transition metal as the central atom formed by the corresponding combination of two main ligands and three auxiliary ligands have been studied theoretically. The electronic structure, frontier molecular orbital, and spin orbit coupling data are used to analyze its application value in light emitting devices. The density functional theory is used to study (tbi)2Ir(bpp), (tbi‐c)2Ir(bpp), (tbi)2Ir(dbm), (tbi‐c)2Ir(dbm), (tbi)2Ir(pic), and (tbi‐c)2Ir(pic). bpp = (2Z)‐3‐hydroxy‐13‐diphenylprop‐2‐en‐1‐one; dbm = 1,3‐di‐phenyl‐1, 3‐propanedione; pic = picolinate. [ABSTRACT FROM AUTHOR]

White organic light-emitting diode (WOLED) containing new blue layer was fabricated with a simple device structure, which is deposited by 4-CbzBiz, Alq3, and DCM2 for blue, green, and red. Electroluminescence (EL) performance of WOLED showed current efficiency (CE) of 0.61 cd/A, power efficiency (PE) of 0.22 lm/W and external quantum efficiency (EQE) of 0.85%. The device exhibited EL max wavelength of 444, 511, and 638 nm. The device showed commission International de l'Eclairage (CIE) value of (0.30, 0.33) corresponding to cool white emission. This result can be used with an advantage in white lighting and display application by obtaining a high color rendering index. [ABSTRACT FROM AUTHOR]

Two new deep-blue chromophores containing hexaphenylbenzene and ethylcarbazole units were synthesized. (E)-9-ethyl-3-(2-(3′,4′,5′,6′-tetraphenyl-[1,1′:2′,1″-terphenyl]-4-yl)vinyl)-9H-carbazole (6P-VC) and 3,3′-((1E,1′E)-(3′,4′,5′,6′-tetraphenyl-[1,1′:2′,1″-terphenyl]-4,4″-diyl)bis(ethene-2,1-diyl))bis(9-ethyl-9H-carbazole) (6P-DVC) showed an ultraviolet-visible absorption at 343 nm and maximum photoluminescence emissions at 417 and 426 nm in solution. Devices doped with 6P-VC and 6P-DVC exhibited a high efficiency of 1.8 and 1.5 cd/A, and external quantum efficiency (EQE) of 3.7 and 1.9%, respectively. The respective devices employing the two materials showed EL maximum wavelengths of 429 and 428 nm. In particular, 6P-VC showed excellent Commission International de l'eclairage Coordinates (CIE) values of (0.16, 0.05). [ABSTRACT FROM AUTHOR]

Two blue emitting materials, 4,4'-(chrysene-6,12-diyl)bis(N,N-diphenylaniline) (TPA-C-TPA) and 12-(4-(diphenylamino)phenyl)-N,N- Diphenylchrysen-6-amine (TPA-C-DPA) were prepared with the composition of chrysene core moiety and dipenylamine (DPA) and triphenylamine (TPA) moieties as the side group. Two compounds were used to emitting layer as the dopants (EMLs) in doped device. The doped device using TPA-C-TPA showed current efficiency of 2.49 cd/A and external quantum efficiency of 4.26% at a current density of 10 mA/cm2. The doped device using TPA-C-DPA exhibited CE of 2.28 cd/A and EQE of 3.52% at a current density of 10 mA/cm2. TPA-C-TPA and TPA-C-DPA show the Commission Internationale de L'Eclairage (CIE) coordinates of (0.15, 0.06) and (0.14, 0.06) corresponding to the electroluminescence peak at 439 and 444 nm. [ABSTRACT FROM AUTHOR]

Utilizing exciplex as the host and fluorescence emitter with dopant materials has been proved successfully to fabricate highly-efficient organic light-emitting diodes. Exciton evolution and energy transfer in this exciplex host–guest system are complex. Gaining insight into the electroluminescence (EL) mechanisms in exciplex-based devices is key for further optimizing device configuration. Here, we have investigated exciton dynamics in devices with exciplex as host and 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran (DCJTB) as red fluorescence emitter. Two exciplexes, 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine (26DCzPPY) doped 2,4,6-tris[3-(triphenylphosphine)phenyl]-1,3,5-triazine (POT2T), and 4,4′,4″-tris[3-methylphenyl(phenyl)amino]-triphenylamine (m-MTDATA) doped tris(8-hydroxyquinoline)aluminum(III) (Alq3), with different band energy are utilized as host materials. Combining the measurements of transient EL, transient photoluminescence and magnetic field effect (MFE), it is concluded that Dexter energy transfer, together with Förster resonance energy transfer, are confirmed in the pure fluorescence doped system. Meanwhile, it is found that DCJTB works with the hot excitons mechanism but not a traditional red fluorescence emitter as recognized previously. This work presents that the transient MFE is powerful for detecting excitonic dynamic processes in excipelx based host–guest EL systems. [ABSTRACT FROM AUTHOR]

Using palladium-catalyzed Suzuki polycondensation, we synthesized new light-emitting fluorene copolymers containing the dicyano derivatives of stilbene and phenanthrene and characterized them by gel permeation chromatography, UV-vis absorption spectroscopy, spectrofluorimetry, and cyclic voltammetry. The photoluminescence spectra of the synthesized polymers show significant energy transfer from the fluorene segments to the dicyanostilbene and 9,10-dicyanophenanthrene units, which is in agreement with the data of theoretical calculations. OLEDs based on these polymers were fabricated with an ITO/PEDOT-PSS (35 nm)/p-TPD (30 nm)/PVK (5 nm)/light emitting layer (70–75 nm)/PF-PO (20 nm)/LiF (1 nm)/Al (80 nm) configuration. Examination of their electroluminescence revealed that copolymers of fluorene with dicyanostilbene show yellow-green luminescence, while polymers with 9,10-dicyanophenanthrene have a greenish-blue emission. The 9,10-dicyanophenanthrene units have a more rigid structure compared to dicyanostilbene and, in OLEDs based on them, an increase in maximum brightness is observed with an increase in the content of the additive to the polymer chain. In particular, the device using fluorene copolymer with 9,10-dicyanophenanthrene (2.5 mol%) exhibited a maximum brightness of 9230 cd/m2 and a maximum current efficiency of 3.33 cd/A. [ABSTRACT FROM AUTHOR]

Developing double boron‐based emitters with extremely narrow band spectrum and high efficiency in organic light‐emitting diodes (OLEDs) is crucial and challenging. Herein, we report two materials, NO‐DBMR and Cz‐DBMR, hinge on polycyclic heteraborin skeletons based on role‐play of the highest occupied molecular orbital (HOMO) energy levels. The NO‐DBMR contains an oxygen atom, whereas the Cz‐DBMR has a carbazole core in the double boron‐embedded ν‐DABNA structure. The synthesized materials resulted in an unsymmetrical pattern for NO‐DBMR and surprisingly a symmetrical pattern for Cz‐DBMR. Consequently, both materials showed extremely narrow full width at half maximum (FWHM) of 14 nm in hypsochromic (pure blue) and bathochromic (Bluish green) shifted emission without losing their high color fidelity. Furthermore, both materials show high photoluminescence quantum yield (PLQY) of over 82 %, and an extremely small singlet‐triplet energy gap (ΔEST) of 0.04 eV, resulting in high reverse intersystem crossing process (kRISC) of 105 s−1. Due to the efficient thermally activated delayed fluorescence (TADF) characteristics, the fabricated OLEDs based on these heteraborins manifested maximum external quantum efficiency (EQEmax) of 33.7 and 29.8 % for NO‐DBMR and Cz‐DBMR, respectively. This is the first work reported with this type of strategy for achieving an extremely narrow emission spectrum in hypsochromic and bathochromic shifted emissions with a similar molecular skeleton. [ABSTRACT FROM AUTHOR]

Developing double boron‐based emitters with extremely narrow band spectrum and high efficiency in organic light‐emitting diodes (OLEDs) is crucial and challenging. Herein, we report two materials, NO‐DBMR and Cz‐DBMR, hinge on polycyclic heteraborin skeletons based on role‐play of the highest occupied molecular orbital (HOMO) energy levels. The NO‐DBMR contains an oxygen atom, whereas the Cz‐DBMR has a carbazole core in the double boron‐embedded ν‐DABNA structure. The synthesized materials resulted in an unsymmetrical pattern for NO‐DBMR and surprisingly a symmetrical pattern for Cz‐DBMR. Consequently, both materials showed extremely narrow full width at half maximum (FWHM) of 14 nm in hypsochromic (pure blue) and bathochromic (Bluish green) shifted emission without losing their high color fidelity. Furthermore, both materials show high photoluminescence quantum yield (PLQY) of over 82 %, and an extremely small singlet‐triplet energy gap (ΔEST) of 0.04 eV, resulting in high reverse intersystem crossing process (kRISC) of 105 s−1. Due to the efficient thermally activated delayed fluorescence (TADF) characteristics, the fabricated OLEDs based on these heteraborins manifested maximum external quantum efficiency (EQEmax) of 33.7 and 29.8 % for NO‐DBMR and Cz‐DBMR, respectively. This is the first work reported with this type of strategy for achieving an extremely narrow emission spectrum in hypsochromic and bathochromic shifted emissions with a similar molecular skeleton. [ABSTRACT FROM AUTHOR]

Organic light-emitting diodes (OLEDs) have been widely used in various fields such as sensors. In this article, we designed six novel heterocyclic Ir(III) complexes: (CFM)2Ir(acac) (named 1 in this paper), (TTIQ)2Ir(acac) (named 2), (CFM)2Ir(tmd) (named 3), (TTIQ)2Ir(tmd) (named 4), (CFM)2Ir(pic) (named 5) and (TTIQ)2Ir(pic) (named 6). The six iridium (III) complexes were calculated using Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT). We studied the bands of the lowest-lying absorptions and lowest energy emissions of complexes 1–6. In addition, we also explored their spectral properties, frontier Molecular Orbital theory(FMO) and spin-orbital coupling value(SOC). Where acac is represented as pentane-2, 4-dione; tmd as 2,2,6,6-tetramethylheptane-3,5-dione; pic as pyridine-2-carboxylate; TTIQ as 1- { thieno[3,2-b]thiophen-2-yl } isoquinoline; CFM as 2-(4-fluorobrobenyl)-4-methylpyridine. A series of heteroleptic cyclometalated Ir (III) complexes, which are used for OLED application, were investigated by DFT and TD-DFT method. The frontier molecular orbital character and charge transfer character shown that they have the advantages of low efficiency roll-off properties, which is a 'stumbling block' in the process of OLED solid-lighting's development. Namely, means the materials will play an important role in the journey development of OLED. [ABSTRACT FROM AUTHOR]

The design of multifunctional materials is a challenging and important objective for a wide array of multidisciplinary applications. However, a multifunctional organic emitter exhibiting simultaneous aggregation‐induced emission (AIE), multi‐responsive polymorphs, mechanoluminescence and electroluminescence have been scarce. In this study, two anthracene based compounds, namely 10‐(4‐(9H‐carbazol‐9‐yl)phenyl)anthracene‐9‐carbonitrile (CzPACN) and 10‐(4‐(di‐p‐tolylamino)phenyl)anthracene‐9‐carbonitrile (DTPACN) was designed and synthesized with rigid and flexible donors, respectively. The CzPACN shows the bright blue emission and DTPACN shows the bright green emission in solution. We have demonstrated an effective strategy to achieve three polymorphic phases such as DTPACN‐α, DTPACN‐β and DTPACN‐γ from DTPACN by controlling the temperature. Under mechanical stimuli, highly restricted and non‐planar crystals of the structurally tuned polymorphs DTPACN‐α, and DTPACN‐β exhibited red shifted emission and DTPACN‐γ showed blue shifted emission. Conversely, CzPACN is not showing polymorphism and is not sensitive to external stimuli. In addition, blue and green OLEDs were fabricated using CzPACN and DTPACN, respectively, as an emitter and achieved a maximum external quantum efficiency (EQEmax) of 5.5% and 5.7%, respectively, for blue and green OLEDs. Further, this study suggests designing multi‐responsive smart materials via a simple modification by introducing a non‐planar unit with a large twist. [ABSTRACT FROM AUTHOR]

Blue emissions in organic light-emitting diodes (OLEDs) are essential for their application in solid-state lighting and full-colour flat panel displays. On the other hand, high-power blue emitters are still uncommon, especially those that can achieve the Commission Internationale de l'Eclairage (CIE, X, Y) coordinates of (0.14, 0.08) in the National Television System Committee (NTSC) blue standard and have high external quantum efficiencies (EQE) of more than 5% because their molecular design presents an enormous challenge. Therefore, creating effective, stable, pure, and deep blue fluorescent materials is vital. Here, it is addressed how useful blue fluorescent Zn (II) complexes are for making organic light-emitting diodes (OLEDs). Utilizing Zn (II) complexes is appealing because of their favourable luminous characteristics, acceptance and mobility, and affordability. This mini-review article aims to provide an overview of Zn (II) complexes that emit blue fluorescent light and have been reported since 2018, while highlighting the unique qualities that make them appropriate OLED materials. [ABSTRACT FROM AUTHOR]

Progression in lighting sources mainly depended on new, robust energy‐efficient diodes due to their advanced photometric properties. All organic light‐emitting sources are constant energy‐efficient devices and will be the light of the future. We explore the potential of transition metal complexes by focusing on cobalt(II), nickel(II), and copper (II) with aminoguanidine naphthoate as white phosphors in organic light‐emitting diodes (OLEDs). The phosphors synthesized at optimized temperature were characterized structurally and thermally by spectral, thermal, and diffraction techniques. The photophysical studies of the target compound in several organic solvents having divergent polarity were also studied, and the results were exhibited. Photometric properties of the complexes were studied using photoluminescence, CIE (Commission internationale de l'éclairage) chromaticity coordinates, correlated color temperature, color purity, Duv, and TLCI (Television Lighting Consistency Index) to verify the applicability of complexes as phosphors. Excellent luminescence property with a high coloring index for (Cu(2NA‐AMG‐2H2O)) opens the advanced avenue for light sources and serves as vital constituents for light‐emitting diodes. [ABSTRACT FROM AUTHOR]

Hidden photophysics is elucidated in the very well‐known thermally activated delayed fluorescence (TADF) emitter, DMAC‐TRZ. A molecule that, based on its structure, is considered not to have more than one structural conformation. However, based on experimental and computational studies, two conformers, a quasi‐axial (QA) and a quasi‐equatorial (QE) are found, and the effect of their co‐existence on both optical and electrical excitation isexplored. The relative small population of the QA conformer has a disproportionate effect because of its strong local excited state character. The energy transfer efficiency from the QA to the QE conformer is high, even at low concentrations, dependent on the host environment. The current accepted triplet energy of DMAC‐TRZ is shown to originate from the QA conformer, completely changing the understanding of DMAC‐TRZ. The contribution of the QA conformer in devices helps to explain the good performance of the material in non‐doped organic light‐emitting diodes (OLEDs). Moreover, hyperfluorescence (HF) devices, using v‐DABNA emitter show direct energy transfer from the QA conformer to v‐DABNA, explaining the relatively improved Förster resonance energy transfer efficiency compared to similar HF systems. Highly efficient OLEDs where green light (TADF‐only devices) is converted to blue light (HF devices) with the maximum external quantum efficiency remaining close to 30% are demonstrated. [ABSTRACT FROM AUTHOR]

Two novel neutral phosphorescent iridium(III) complexes (Ir1 and Ir2) were rationally designed and synthesized with high yields using 10,11,12,13-tetrahydrodibenzo[a,c]phenazine as the main ligand. The two complexes showed bright-red phosphorescence (625 nm for Ir1, and 620 nm for Ir2, in CH2Cl2), high-luminescence quantum efficiency (0.32 for Ir1, and 0.35 for Ir2), obvious solvatochromism and good thermostability. Then, they were used to fabricate high-efficiency red OLEDs via vacuum evaporation; the maximum current efficiency, power efficiency, and external quantum efficiency of the red devices based on Ir1 and Ir2 are 13.47/15.22 cd/A, 10.35/12.26 lm/W, and 10.08/7.48%, respectively. [ABSTRACT FROM AUTHOR]

Macrocycles have attracted significant attention from academia due to their various applications in organic field-effect transistors, organic light-emitting diodes, organic photovoltaics, and dye-sensitized solar cells. Despite the existence of reports on the application of macrocycles in organic optoelectronic devices, these reports are mainly limited to analyzing the structure–property relationship of a particular type of macrocyclic structure, and a systematic discussion on the structure–property is still lacking. Herein, we conducted a comprehensive analysis of a series of macrocycle structures to identify the key factors that affect the structure–property relationship between macrocycles and their optoelectronic device properties, including energy level structure, structural stability, film-forming property, skeleton rigidity, inherent pore structure, spatial hindrance, exclusion of perturbing end-effects, macrocycle size-dependent effects, and fullerene-like charge transport characteristics. These macrocycles exhibit thin-film and single-crystal hole mobility up to 10 and 26.8 cm2 V−1 s−1, respectively, as well as a unique macrocyclization-induced emission enhancement property. A clear understanding of the structure–property relationship between macrocycles and optoelectronic device performance, as well as the creation of novel macrocycle structures such as organic nanogridarenes, may pave the way for high-performance organic optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this work, we investigated the potential for phosphorescent emitters to achieve the BT.2020 color standard in displays, where the CIE coordinates for red and green are (0.709, 0.292) and (0.170, 0.797), respectively. Optical simulations were performed for both green and red top emission organic light emitting devices (OLEDs). For the green emitter, it is possible to reach (0.170, 0.785) using a spectrum with a peak wavelength (λmax) at 526 nm and a full width at half maximum (FWHM) less than 30 nm. For the red emitter, in order to achieve (0.708, 0.292) while maintaining a high current efficiency (CE), it is important to decrease the FWHM instead of red‐shifting the spectrum. Following the guidance of these simulation results, we designed and synthesized novel deep green (DGD) and deep red phosphorescent (DRD‐II) emitters. The photoluminescent (PL) spectrum of DGD shows an FWHM of 30 nm and a λmax of 523 nm. A top‐emission green OLED built using DGD reached a CE of 171 cd/A at an operating voltage of 3.3 V and a lifetime of 95% of initial brightness (LT95) > 1300 h at 10 mA/cm2 with a CIE (x, y) = (0.170, 0.777). This is, to our knowledge, the best device performance ever reported for a green phosphorescent OLED at this CIE y. The PL spectrum of DRD‐II has a λmax of 630 nm with an FWHM of 30 nm. A top‐emission red OLED built with DRD‐II achieved a CE of 59 cd/A, an operating voltage of 3.2 V and an LT95 over 20,000 h at a drive current of 10 mA/cm2 with a CIE (x, y) = (0.708, 0.292). We also studied the angular dependence of the above devices and found they were comparable to devices with commercial emitters for the Digital Cinema Initiative P3 (DCI‐P3) standard that had a wider FWHM. Combining these green and red emitters with a commercial blue OLED at (0.131, 0.046), we are able to cover 97% of the BT.2020 color gamut. The results using DGD and DRD‐II suggest that they have great potential to satisfy BT.2020 in an organic phosphorescent system. [ABSTRACT FROM AUTHOR]

We present a novel pixel design called TurboLED® for reducing the power consumption of displays, as well as extending lifetime and expanding color gamut. In a TurboLED® display, each pixel comprises stacked LEDs, with independent lighter and deeper red, green and blue emissive units. We demonstrate 36.9% power savings for a TurboLED® display compared to a standard RGB OLED display. With further optimization, there is potential to reduce display power consumption by up to 50% and enable the Rec. 2020 color gamut without significant increase in power consumption. [ABSTRACT FROM AUTHOR]

In this work, a new luminescent material of a small-molecule stilbene derivative (BABCz) containing anthracene was designed and synthesized by three simple reactions. The material was characterized by 1H-NMR, FTMS, and X-ray and tested using TGA, DSC, UV/Vis, fluorescence spectroscopy, and atomic force microscopy. The results demonstrate that BABCz has luminescence properties with good thermal stability and can be doped with 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) to prepare highly uniform films, which allows the fabrication of OLED devices with ITO/Cs2CO3:BABCz/CBP:BABCz/MoO3/Al configuration. This simplest device in the sandwich structure emits green light at 6.6–12 V and has a brightness of 2300 cd/m2, indicating the potential of this material in OLED manufacturing. [ABSTRACT FROM AUTHOR]

Infrared (IR)‐to‐visible up‐conversion device allows a low‐cost, pixel‐free IR imaging over the conventional expensive compound semiconductor‐based IR image sensors. However, the external quantum efficiency has been low due to the integration of an IR photodetector and a light‐emitting diode (LED). Herein, by inducing a strong micro‐cavity effect, a highly efficient top‐emitting IR‐to‐visible up‐conversion device is demonstrated where PbS quantum dots IR‐absorbing layer is integrated with a phosphorescent organic LED. By optimizing the optical cavity length between indium tin oxide (ITO)/thin Ag/ITO anode and semi‐transparent Mg:Ag top cathode, the up‐conversion device yields 15.7% of photon‐to‐photon conversion efficiency from the top‐emission. The high efficiency can be achieved under a low IR transmission through the semi‐reflective anode. Finally, pixel‐free IR imaging is demonstrated using the up‐conversion device, boosting the effect of micro‐cavity on the brightness and the contrast of an IR image. [ABSTRACT FROM AUTHOR]

Electrodeposition is an old and effective method for the fabrication of organic films. Though electrodeposited organic films have been widely used in various applications, highly luminescent films have been a great challenge because the electrochemically doped state may strongly quench the fluorescence. In the first part of this review, the organic electrodeposition techniques, along with general electropolymerization and other special electrodepositions are introduced. In the second part of the review, we describe how to electrochemically fabricate luminescent films for organic light-emitting diodes (OLEDs). With the rational molecular design and well-controlled electrodeposition process, we have not only demonstrated high-performance OLEDs, but also paved a promising way to practice active-matrix OLEDs (AMOLEDs) and super-resolution OLEDs. In particular, RGB 3 × 3 array OLEDs based on active-matrix substrates, RGB passive-matrix OLEDs (PMOLEDs) with a resolution of 210 ppi, and monochromatic OLEDs with a super-resolution of 2822 ppi have been successfully fabricated. It is highly anticipated that the organic electrodeposition technology is of comparable or perhaps even higher contenders in manufacturing and downscaling OLEDs and AMOLEDs with low-cost and high-resolution for the human-computer interaction fields such as augmented reality (AR), virtual reality (VR), etc. [ABSTRACT FROM AUTHOR]

In this study, we have carried out a theoretical study on six organic compounds based on thiophene and carbazole, with the aim of using them as a hole‐injecting layer of organic light‐emitting diodes (OLEDs). In this study, we have tested two types of structures: D‐π‐D for MO1, MO2, MO3, and MO4 compounds and D‐π‐A for MO5 and MO6 compounds. The correlation structure‐properties of these studied compounds have been proceeded and discussed by analyzing highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), energy gap, polarization effect, atom transition density matrix, absorption, and photoluminescence (PL). This theoretical study, based on density functional theory (DFT)/TPSSTPSS/aug‐cc‐pVQZ and the integral‐equation‐formalism polarizable continuum model/Coulomb attenuated method‐Becke, 3‐parameter, Lee–Yang–Parr (IEFPCM/TD‐CAM‐B3LYP)/6‐31++G(d,p) is consolidated by experimental data for MO1, MO2, and MO4 compounds, allowing the determination of their structural and optoelectronic properties (HOMO, LUMO, gap [Eg], absorption, and emission parameters). The obtained results appear very conclusive and show that the performance of these compounds in terms of luminescence, absorption, and current–voltage (I–V) characteristics of OLED devices make them a promising candidate for the realization of light‐emitting diodes. [ABSTRACT FROM AUTHOR]