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Conjugated polymers are an important class of chromophores for optoelectronic devices. Understanding and controlling their excited state properties, in particular, radiative and non‐radiative recombination processes are among the greatest challenges that must be overcome. We report the synthesis and characterization of a molecularly encapsulated naphthalene diimide‐based polymer, one of the most successfully used motifs, and explore its structural and optical properties. The molecular encapsulation enables a detailed understanding of the effect of interpolymer interactions. We reveal that the non‐encapsulated analogue P(NDI‐2OD‐T) undergoes aggregation enhanced emission; an effect that is suppressed upon encapsulation due to an increasing π‐interchain stacking distance. This suggests that decreasing π‐stacking distances may be an attractive method to enhance the radiative properties of conjugated polymers in contrast to the current paradigm where it is viewed as a source of optical quenching. [ABSTRACT FROM AUTHOR]

Conjugated polymers are an important class of chromophores for optoelectronic devices. Understanding and controlling their excited state properties, in particular, radiative and non‐radiative recombination processes are among the greatest challenges that must be overcome. We report the synthesis and characterization of a molecularly encapsulated naphthalene diimide‐based polymer, one of the most successfully used motifs, and explore its structural and optical properties. The molecular encapsulation enables a detailed understanding of the effect of interpolymer interactions. We reveal that the non‐encapsulated analogue P(NDI‐2OD‐T) undergoes aggregation enhanced emission; an effect that is suppressed upon encapsulation due to an increasing π‐interchain stacking distance. This suggests that decreasing π‐stacking distances may be an attractive method to enhance the radiative properties of conjugated polymers in contrast to the current paradigm where it is viewed as a source of optical quenching. [ABSTRACT FROM AUTHOR]

Thermally activated delayed fluorescence (TADF) materials have continued to attract interest due to their rapid improvements in efficiency, non-toxic and potential to be manufactured at energy-saving organic light-emitting diode for full-color display and solid-state lighting. Here, The bipolar and electroluminescence (EL) characteristics of TADF host, 11-(3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-12,12-dimethyl-11,12-dihydroindeno[2,1- a ]carbazole (DPDDC), were investigated. By incorporating the phosphorescent tris[2-(p -tolyl)pyridine]iridium(III) [Ir(mppy) 3 ] dopant into the matrix, DPDDC showed more excellent EL performance compared with the typical 4,4′-bis(N -carbazolyl)-1,1′-biphenyl (CBP) host. The turn-on voltage for phosphorescent organic light-emitting diodes (PhOLEDs) was decreased to 2.2 V from 2.5 V by exploiting the TADF host instead of CBP. Crucially, we found that the ratio of Ir(mppy) 3 in TADF host plays a significant role in EL process. Remarkable low efficiency roll-off was achieved with above 90% of the current efficiency maintained even at a brightness of 3000 cd m−2, along with high power efficiency of 84.8 lm·W−1 and the external quantum efficiency of 20.6% for DPDDC: 5 wt% Ir(mppy) 3 -based device. Phosphorescent organic light-emitting diodes with low extremely turn-on voltage and high power efficiency by incorporating phosphorescent tris[2-(p -tolyl)pyridine]iridium(III) [Ir(mpppy) 3 ] dopant into TADF host. [Display omitted] • TADF host with bipolar (electron/hole) transport characteristics and excellent electroluminescence performance were investigated. • Turn-on voltage of green PhOLED as low as 2.2 V by exploiting TADF host. • State-of-the art PhOLED exhibited high power efficiency of 84.8 lm·W−1, maximum EQE of 20.6% and efficiency roll-off of 6% at 1000 cd m−2. [ABSTRACT FROM AUTHOR]

Solution-processed perovskite light-emitting diodes (PeLEDs) show great potential for low-cost fabrication of large-area display panel, however, large crystallinity and poor film coverage generally cause high operating voltage and low luminescence efficiency in all solution-processed PeLEDs, and thus limiting their commercial applications. Here, the phenylpropylammonium bromide (PPABr) as ligand additive in MAPbBr 3 for improving perovskite film quality and the device performance of PeLEDs are reported. With varying additive ratios of PPABr, the morphological changes and photoluminescence properties of perovskite film were investigated. Benefiting from precisely managing the ratio, the PPABr-based perovskite films exhibited well-defined crystal phase and high photoluminescence intensity. As a result, all solution-processed MAPbBr 3 PeLEDs with the optimized concentration of PPABr showed a low turn-on voltage of 2.2 V and a maximum device luminance of 13,666 cd/m2, which are comparable to the non-additive device (with turn-on voltage and luminance of 3.0 V and 2910 cd/m2). Notably, an approximately 5.5-fold improvement for 0.09 mol PPABr-based device in current efficiency was achieved compared to the pristine MAPbBr 3 PeLED. High performance all solution-processed perovskite light-emitting diodes by incorporating long ligand the phenylpropylammonium bromide as additives into MAPbBr3 layer. [Display omitted] • High performance all solution-processed PeLEDs were designed and fabricated. • PPABr as additives for MAPbBr 3 significantly enhance the crystalline phase and PL properties of thin film. • State-of-the-art MAPbBr 3 PeLEDs exhibited ultra-low turn-on voltage of 2.2 V. • An approximately 5.5-fold improvement in current efficiency was achieved for the PPABr-based device. [ABSTRACT FROM AUTHOR]

We have systematically investigated hole/electron distribution and exciton dynamics in blue fluorescent and yellow phosphorescent organic light-emitting diodes (OLEDs). We demonstrate that the importance of appropriate charge carrier confinement and exciton management for the realization of highly efficient and stable OLEDs. For yellow phosphorescent device based on Ir(MePQ)2(acac), we have studied the behavior of various intrinsic emission zones on the characteristics of OLEDs with the hole/electron-transporting matrix. The current efficiency increases from 15.7 to 31.7 cd A−1 with the rise in electron-transporting matrix from 20 to 80 nm. We attributed the improved performance to the strong hole-transfer capabilities and relatively weak electron-donating abilities of Ir-complex doped transporting matrix. In contrast, the efficiencies of blue devices decreased with increasing emitting layer (EML), suggesting that the rate of hole-electron pair recombination continuously decrease with the increasing EML thickness due to blue fluorescent dopant hindering hole transfer. In addition, the complementary-color white OLEDs (WOLEDs) with various EML thickness were also demonstrated. Based on their performance, we have found that the use of thin EML in WOLEDs can significantly improve optoelectronic conversion efficiency, whereas deteriorated device properties reversely. [ABSTRACT FROM AUTHOR]

The emergence of wearable electronics and optoelectronics requires the development of devices that are not only highly flexible but can also be woven into textiles to offer a truly integrated solution. Here, we report a colour-tunable, weavable fibre-shaped polymer light-emitting electrochemical cell (PLEC). The fibre-shaped PLEC is fabricated using all-solution-based processes that can be scaled up for practical applications. The design has a coaxial structure comprising a modified metal wire cathode and a conducting aligned carbon nanotube sheet anode, with an electroluminescent polymer layer sandwiched between them. The fibre shape offers unique and promising advantages. For example, the luminance is independent of viewing angle, the fibre-shaped PLEC can provide a variety of different and tunable colours, it is lightweight, flexible and wearable, and it can potentially be woven into light-emitting clothes for the creation of smart fabrics. [ABSTRACT FROM AUTHOR]

We have investigated the photoluminescent characteristics of binaphthyl derivates, 4′′,4′′′- N, N-diphenylamine-4,4′-diphenyl-1,1′-binaphthyl (BN1), 4′′, 4′′′-(9-(9H-9-carbazole)-4, 4′-diphenyl-1, 1′-binaphthyl (BN2) and 4, 4′-bis(9-( p-fluorophenyl)-9H-3-carbazole))-1, 1′-binaphthyl (BN3) and found their amplified spontaneous emission (ASE) from neat films. The ASE threshold of pumping energy, Eth = 4.4, 3.8, 5.3 µJ cm−2 were obtained under optical excitation at 355 nm for the neat films of BNs, 1, 2, and 3, respectively. Moreover, the lasing of those non-doped films exhibited deep-blue emission, whose peak spectra of BNs 1, 2, and 3 were 438, 421, and 428 nm, respectively. We have also studied the thermal-stability of BN1 by annealing at 250 °C for 30 min and found that the ASE threshold stayed almost unchanged compared to untreated film, demonstrating its high heat resistance characteristics. The characteristics of decreased tendency to crystallize and weaker intermolecular interactions in the solid state of BNs make them potential candidates for approaching electrically pumped organic laser diodes. [ABSTRACT FROM AUTHOR]

We have employed the photoluminescent (PL) spectrum of an accelerated aging organic light-emitting diode (OLED) to investigate the mechanisms of molecular decomposition in the whole and each organic functional layer using a bevel-cutting and peel-off method. The devices were operated at a constant current density of 37 mA/cm2 and 70 °C until the luminance reached a half of the initial luminance. The results show a slight or even negligible degradation in PL intensity compared to unbiased devices, indicating that little cracked molecular structure and destroyed host-guest transfer mechanism occurred in organic materials of the biased device Scanning electron microscopy images of devices with bias demonstrated that the delamination at the interfaces of organic layers/Al and light-emitting layer/hole transport layer occurs. We concluded that the charges accumulated at the interface of the heterojunction formed between adjacent organic layers with different energy barriers in or near the emissive layer, as well as the cathode/organic layer, should be mainly responsible for the degradation of OLEDs. [ABSTRACT FROM AUTHOR]

Despite considerable interest, uniform and robust flexible transparent conducting electrodes (FTCEs) that can be seamlessly integrated and used for highly efficient large‐area flexible oganic light‐emitting diodes (OLEDs) remain elusive. In this study, a large‐area fabrication of uniform transparent electrodes for high‐performance flexible OLEDs by exploiting the rapid nanowelding process of silver nanowires (AgNWs) onto polyethylene terephthalate substrate under Xe‐lamp irradiation and mechanical pressing treatment is reported. The performance of AgNWs FTCEs is significantly enhanced by applying the Xe‐lamp beam irradiation for 5 s and subsequent compression at 20 MPa for 15 s, achieving a low sheet resistance of 26.5 Ω sq−1, a high transmittance of 95.2% (at 550 nm), and very smooth surfaces with root‐mean‐square of 5.4 nm. Meanwhile, the nanowelded AgNWs FTCEs maintain excellent electrical conductivity (only a 2.96% increase in ΔR/R0) after 1000 bending cycles. The resulting AgNWs FTCEs‐based green phosphorescent OLED achieves an unprecedented external quantum efficiency (EQE) of 23.7% and a current efficiency as high as 81.5 cd A−1. Benefiting from the uniform properties for resulting AgNWs FTCEs, the fabricated flexible OLED with a large area of 25 × 25 mm2 still retains a high EQE of 22.2% and a current efficiency of 78.0 cd A−1. [ABSTRACT FROM AUTHOR]

A new family of bipolar fluorinated 3,3′-dimethyl-9,9′-bianthracene derivatives (MBAnFs) have been synthesized, characterized and applied as deep-blue emitters and host materials in fluorescent organic light-emitting devices (OLEDs). Fine tuning the emission characteristics could be achieved by varying the position and the number of the F substituents on the two phenyl rings attached to MBAn core. Remarkably, 10,10′-bis(4-fluorophenyl)-3,3′-dimethyl-9,9′-bianthracene (MBAn-(4)-F)-based OLEDs showed an excellent performance. Both non-doped and doped multilayer OLEDs based on MBAn-(4)-F achieved the maximum external quantum efficiency (EQE max ) of 6.11% and 6.65% with Commission Internationale de L'Eclairage (CIE) coordinates of (0.155, 0.058) and (0.153, 0.055), respectively, matching the requirement of European Broadcasting Union standard of CIE (0.15, 0.06) very well. Furthermore, when doping blue-emitting p -bis( p -N,N-diphenyl-aminostyryl)-benzene (DSA-ph) into MBAn-(4)-F as a light-emitting layer (EML), the device achieved an astonishing current efficiency of 23.01 cd A −1 and a record-setting EQE of 11.52% with negligible efficiency roll-off, compared with other DSA-ph-based OLEDs. These results are attributed to the well-controlled bipolar characteristic of the MABn-(4)-F, leading to a better charge balance in the EML. In addition, the combination of the locally emissive component and twisted intramolecular charge-transfer component in one excited state can significantly enhance the singlet generation fraction in OLEDs. [ABSTRACT FROM AUTHOR]

Adaptive Rear-lighting System (ARS) in stoplight has been widely used in various vehicles to catch following drivers' attention with special information about light brake, heavy brake and slamming brake, which greatly improves traffic safety. However, most of the existing vehicle ARS usually employ multi light source, leading to complicated layout, circuit and bulky module and high current drain, resulting in high cost. Recently, ARS based on organic light-emitting diodes (OLEDs) as single light source has attracted attention as a competitive alternative to the conventional ARS. The OLEDs are known for their lower lost, environment protection, broad adjustability and color range, lightness and simple product process. Herein, we designed an advanced ARS based on single OLED module, automatically adjusting the color of stoplight among light red, pure red, deep red in accordance with light brake, heavy brake and slamming brake, respectively. This novel ARS for a vehicle stoplight includes the brake pedal assembled with pressure sensor and an OLED module. [ABSTRACT FROM AUTHOR]

Inverted organic light-emitting diodes (IOLEDs) have great potential application in flat-panel display. In this study, a lithium (Li) ion doped solution processed zinc oxide (Li-ZnO) layer was employed as the cathode buffer layer (CBL) for IOLEDs. The Li-ZnO CBL was prepared by inducing the Li ion of 8-hydroxyquinolatolithium (Liq) to diffuse into ZnO film through thermal annealing the bi-layer ZnO/Liq film. Based on the Li-ZnO CBL with ultraviolet(UV) treatment, the IOLED using tris(8-hydroxyquinoline) aluminum as the emitting layer possessed an optimal current efficiency of 4.42 cd A−1, which was improved by 55% than those of the devices with neat ZnO as CBL. The enhancement of the device performance could be attributed to the enhanced electron mobility and electron injection ability of the Li-ZnO CBL. Our finding indicates that the low-temperature deposited Li-ZnO film has great potential for the application of OLED display. [ABSTRACT FROM AUTHOR]

This work demonstrates a novel transparent electrode using embedded Al grids fabricated by a simple and cost-effective approach using photolithography and wet etching. The optical and electrical properties of Al grids versus grid geometry have been systematically investigated, it was found that Al grids exhibited a low sheet resistance of 70 Ω □ −1 and a light transmission of 69% at 550 nm with advantages in terms of processing conditions and material cost as well as potential to large scale fabrication. Indium Tin Oxide-free green organic light-emitting diodes (OLED) based on Al grids transparent electrodes was demonstrated, yielding a power efficiency >15 lm W −1 and current efficiency >39 cd A −1 at a brightness of 2396 cd m −2 . Furthermore, a reduced efficiency roll-off and higher brightness have been achieved compared with ITO-base device. [ABSTRACT FROM AUTHOR]

Abstract: The carrier transfer and luminescence characteristic of concentration-dependent tris(2-phenylpyridine) iridium (Ir(ppy)3) doped in 4,4′-bis(carbazol-9-yl)-biphenyl (CBP) film of 40nm have been investigated. Based on the charge-only devices with different concentration of Ir(ppy)3:CBP, we have found that an increasing dopant concentration can facilitate hole transfer, whereas suppress electrons transfer reversely. The ratio of Ir(ppy)3 in CBP plays a significant role in energy transfer process. Results have shown that excess Ir(ppy)3 possessed a shortened fluorescence lifetime, indicating a concentration quenching effect in Ir(ppy)3:CBP film. The performance of the device decreased rapidly with increasing of doping concentration of Ir(ppy)3 in CBP. A high efficiency of 65.2cd/A with low efficiency roll-off phosphorescent OLED was achieved, in which 10wt%Ir(ppy)3 in CBP was light-emitting layer. [Copyright &y& Elsevier]

Organic light-emitting diode (OLED) is an electroluminescent technology that relies on charge-carrier dynamics and is a potential light source for variable environmental conditions. Here, by exploiting a self-developed low-temperature testing system, we investigated the characteristics of hole/electron transport, electro-optic conversion efficiency, and operation lifetime of OLEDs at low-temperature ranging from –40 °C to 0 °C and room temperature (25 °C). Compared to devices operating at room temperature, the carrier transport capability is significantly decreased with reducing temperature, and especially the mobility of the hole-transporting material (HTM) and electron-transporting material (ETM) at –40 °C decreases from 1.16 × 10−6 cm2/V⋅s and 2.60 × 10−4 cm2/V⋅s to 6.91 × 10−9 cm2/V⋅s and 1.44 × 10−5 cm2/V⋅s, respectively. Indeed, the temperature affects differently on the mobilities of HTM and ETM, which favors unbalanced charge-carrier transport and recombination in OLEDs, thereby leading to the maximum current efficiency decreased from 6.46 cd⋅A−1 at 25 °C to 2.74 cd⋅A−1 at –40 °C. In addition, blue fluorescent OLED at –20 °C has an above 56% lifetime improvement (time to 80% of the initial luminance) over the reference device at room temperature, which is attributed to efficiently dissipating heat generated inside the device by the low-temperature environment. [ABSTRACT FROM AUTHOR]

[Display omitted] • In 2 O 3 film is used as an electron transport layer in Perovskite Solar Cells. • The In 2 O 3 electron transport layer is prepared by electron beam evaporation. • In 2 O 3 layer can improve the film formation quality and crystallinity of perovskite. • The photovoltaic performance of perovskite solar cells is enhanced by In 2 O 3 layer. In perovskite solar cells, the interface plays a crucial role in photovoltaic performance because excitons dissociate and compound at the interface. In this paper, the optical absorption layer of In 2 O 3 planar perovskite solar cells is studied, which is an efficient intermediate layer between the TiO 2 electron transport layer and perovskite. The modification of the In 2 O 3 interlayer increases the average power conversion efficiency from 6.74% to 10.68%. Based on this background, some other feature descriptions are also carried out. The results show that the photovoltaic performance can be improved by depositing the In 2 O 3 interlayer, mainly due to the improved film morphology, reduced recombination center, bulk carrier concentration and Hall mobility. It has been shown that In 2 O 3 can be used as an efficient interface material on all-inorganic perovskite solar cells. [ABSTRACT FROM AUTHOR]

Abstract The development of white organic light-emitting diodes (WOLEDs) holds great promise for the production of high-color-quality lighting sources. High quantum efficiencies for the conversion of electrical energy to light have been realized. The color stability and color-rendering index (CRI) become bottleneck for the commercial application of WOLEDs. Here, we employed a metal-free dimerization of 1‑phenyl‑3,5‑diamine‑triazine (DPDT) as a single non-doped emitter in WOLEDs, that exhibits mild efficiency roll-off while maintaining CRI of 92. This high CRI is attributable to the DPDT with efficient monomer and excimer emission, which together emit a relatively wide spectrum that nearly covers the entire range of visible light. The formation of the excimer can make the emission color of single-emitter based WOLEDs tunable with the applied bias over a wide range from blue to pure white. Highlights • The metal-free dimerization of 1-phenyl-3,5-diamine-triazine (DPDT) materials were synthesized. • The emission color can be tuned over a wide range from blue to pure white. • The resulting color tunable WOLEDs achieves mild efficiency roll-off while maintaining CRI of 92. [ABSTRACT FROM AUTHOR]

Abstract A series of alkyl substituted 9,9′-bianthracene derivatives (BAs) with easy availability and low cost have been applied as deep-blue emitters and blue host materials in fluorescent organic light-emitting diodes (OLEDs). The nearly perpendicular geometry configuration of 9,9′-bianthracene and the additional alkyl units with large steric hindrance in methyl substituted MBA and tert- butyl substituted TBBA would reduce the aggregation formation emitting at longer wavelength by intramolecular and intermolecular interaction, which endows both of the compounds with good thermal properties, and film-forming abilities as well as excellent electroluminescence performance. Nondoped pure deep-blue OLED using TBBA as the emitter showed good performance with EQE of 3.20% and high color purity with CIE (0.15, 0.06), which matched the EBU standard blue very well. Furthermore, these BAs worked as excellent host materials for p -bis(p - N,N -diphenyl-aminostyryl)benzene (DSAph) dopant to get high-performance OLEDs with low turn-on voltages and high efficiencies, especially for MBA bearing two methyl substituents at 3- and 3′-positions of the 9,9′-bianthracene as the fluorescent host with a low turn-on voltage of 3.0 V, a high current efficiency of 16.54 cd/A and a high EQE of 9.47% with unobservable efficiency roll-off. Particularly, EQE can be maintained over 9.20% with very little variation of 0.54% in the range of luminance value of 1.54–13800 cd/m2 for the MBA-based device. The improved EQEs are due to the enhanced occurrence of singlet excitons in BAs-based devices. Graphical abstract Image 1 Highlights • Alkyl substituted 9,9'-bianthracene derivatives (BAs) with easy availability and low cost. • Nondoped TBBA-based blue OLED showed EQE of 3.20% with excellent CIE (0.15, 0.06). • EQE maintained over 9.24% with very little variation of 0.54% in the range of luminance 1.54–13800 cd/m2 for MBA:DSAph-based device. [ABSTRACT FROM AUTHOR]

Abstract Top-emission flexible organic light-emitting devices (TE-FOLEDs) are highly suitable for next generation display due to their numerous assets including top-emitting configuration and mechanical flexibility. One major challenge in TE-FOLEDs is to prepare a deformable and reflective bottom electrode capable of effective carrier injection. In this paper, a new strategy for efficient and foldable TE-FOLEDs is demonstrated. It is based on a highly conductive Ag-nanoparticles (Ag-NPs) modified graphite that is used as a flexible bottom electrode. The good reflectance to full-color emission (>59% over the whole visible wavelength range), ultralow sheet resistance (<5 Ω/sq), and high tolerance to mechanical bending (almost unchanged in resistance after bending 1000 times with an angle of ±90°) of the modified graphite synergistically constitute a breakthrough in the domain of TE-FOLEDs. The maximum current efficiencies reach 15.0, 50.2, 16.8 cd/A for red, green, blue emissions, respectively. Colorimetric gamut increased by 99.6% compared to bottom emission structure with the corresponding Commission Internationale de L'Eclairage (CIE) coordinates of the red/green/blue (R/G/B) devices. In particular, the TE-FOLEDs incorporating highly flexible graphite electrodes offer great mechanical durability and the initial brightness of 5000 cd/m can be maintained over 90% after bending for 1000 bending cycles. This approach is expected to open a new avenue for developing foldable displays. Graphical abstract Image 1 Highlights • The Ag nanoparticles modified graphite onto PET substrate was fabricated with high flexibility and good heat dissipation. • The R/G/BTE-FOLEDs exhibit high color purity and enhanced colorimetric gamut compared to bottom-emitting devices. • The high current efficiency of 15.0, 50.2 and 16.8 cd/A were achieved for R/G/B TE-FOLEDs with low efficiency roll-off. • The TE-FOLEDs show high flexibility after bending for 1000 cycles at the initial brightness of 5000cd/m2. [ABSTRACT FROM AUTHOR]

This paper demonstrates the use of multiple polyethyleneimine (PEI) films acting as interface layers in the inverted organic light-emitting diodes (OLEDs) to solve the mixing problem between different functional layers. The morphological, electrical and photoluminescence characteristics of PEI films are systematically investigated. The thickness of PEI layers is optimized to achieve both good electron transport and ability of preventing the miscibility. The authors' results show that the insertion of double PEI interface layers in the inverted OLEDs allow the deposition of electron transport layer and emissive layer all in solution. Finally, the authors report an inverted green OLED with one and double PEI interface layers. The green OLED with double PEI interface layers yields a maximum current efficiency of 45.2 cd A-1, which is close to the device using thermal deposition method. The authors thus believe that the application of multiple PEI interface layers could provide a promising way to obtain highly efficient OLEDs in solution processing. [ABSTRACT FROM AUTHOR]

We have systematically investigated the temperature-dependent device performance of organic photovoltaic (OPV) cells based on a squaraine dye. The 2,4-bis[4-( N , N -diisobutylamino)-2,6-dihydroxyphenyl] squaraine:[6,6]-phenyl C 71 butyric acid methyl ester (DIBSQ:PC 70 BM) OPV devices were fabricated and characterized under 100 mW cm −2 (AM1.5G solar spectrum) in a temperature range from 285 to 360 K. The temperature-dependent photovoltaic parameters such as open-circuit voltage ( V oc ), short-circuit current density ( J sc ), fill factor (FF) and power conversion efficiency (PCE) were studied in detail. The increasing temperature led to an improvement of J sc and FF, which should be ascribed to the enhanced carrier mobilities and improved electrode/active layer contact thus the improvement of photocurrent extraction at an elevated temperature. However, the V oc decrease in the same period due to the carrier recombination of the OPV device. The increase in the J sc and FF overtakes the decrease in the V oc with increasing temperature, resulting in a significantly improved PCE at elevated temperature. This study indicated that the DIBSQ based BHJ cells has promising potential for the practical application under changeable temperature environment. [ABSTRACT FROM AUTHOR]

White organic light-emitting diodes (WOLED) with inorganic/organic/hybrid nanolaminate distributed Bragg reflector (DBR) prepared by atomic layer deposition (ALD) has been firstly developed, and the improved structural, optical, and electrical properties have been observed. The functional layer consists of periodically alternating layers of ZrO 2 /Zircone (zirconium alkoxides with carbon-containing backbones) films fabricated using ALD. By well adjusting the thickness and emissive dyes of the emission layer, three white light diodes were realized based on three cavity modes with different resonance wavelength and intensity. The narrowed lectroluminescent (EL) spectra from the microcavity organic light emitting diodes (MOLEDs) are of high-purity, and the off-resonant optical mode is highly suppressed due to the excellent optical properties of the DBR layers with high reflectivity in a wide stop-band range. The CIE chromaticity coordinates of devices are tuned from (0.33, 0.34), (0.43, 0.40) to (0.57, 0.40), which are all on the planckian locus, and the color temperature is adjusted from 5783 K, 3842 K to 2245 K. This work exhibits a simple and novel approach to achieve a sunlight-like WOLED by constructing the inorganic/organic nanolaminate DBR using ALD, which will be very important for healthy display and lighting. [ABSTRACT FROM AUTHOR]

Light extraction efficiency of organic light emitting diode (OLED) was enhanced by attaching a thin film with inverted-pyramid texture onto a glass substrate. Two groups of polyvinyl alcohol (PVA) films with differently shaped inverted-pyramid texture were fabricated by a simple transferring imprint approach, and their effects on light extraction of OLED were studied. We found out that the light extraction was affected mainly by the inclination angle rather than size of inverted-pyramid, which was explained by the classic ray theory as well. Besides, the textured film brought hardly changed emission spectrum and wider viewing angle of the OLED. [ABSTRACT FROM AUTHOR]

Highlights: [•] A very simple printing and transferring process for improving OLEDs performances. [•] A pyramid-based texture film was introduced to OLEDs and proved efficiency. [•] The pyramid-based structure was introduced from solar cells. [•] This method is simple and effective without any side effects. [Copyright &y& Elsevier]

Organic Light-Emitting Diodes Organic light‐emitting diode (OLED) is a potential light source for variable harsh environments ranging from external ornament pasting to fascinating space travel and deep‐sea exploration under high pressure. In article number 2100120, Saihu Pan, Kunping Guo, Bin Wei, and co‐workers study the influence of external pressure on the specific organic functional layer and the whole OLEDs for their electrical and electroluminescence characteristics. It is worth noting that the green fluorescence OLED with a >12% increase in current efficiency by applying pressure of 0.75 MPa for 10 min with respect to the device without pressure treatment. Most interestingly, highly stable OLEDs with long operation lifetime are achieved by specific pressure condition, indicating positive effects of pressure treatment on device stability. Envisioning a bright future, it is reasonable to expect that this study provides a new strategy and insights for material development and high‐performance OLED application under extreme pressure conditions. [ABSTRACT FROM AUTHOR]

Intermolecular interactions arise from molecular aggregation and cause concentration quenching and excimer emission. Although aggregation or excimer induced emission are sometimes favored, for example for colour tuning, intermolecular interactions should usually be minimized because concentration quenching and excimer emission usually result in poor efficiency and colour instability. In this paper, two novel tert-butyl modified naphthyl derivates, 4,5′-di-{[N,N,N′,N′- tetrakis-(4-tert- butyl-phenyl)]phenyl-1″,4‴-diamine}-1,1′-binaphthalenyl (BN5) and 1,5-di-{[N,N,N′, N′-tetrakis-(4-tert-butyl-phenyl)]phenyl-1″,4‴-diamine}-3,7-bi-tertbutylnaphthalenyl (BN6), have been synthesized and their intriguing photophysical properties and high-efficiency deep-blue electroluminescence (EL) in less-concentrated condensed phase were investigated. Electroluminescent devices based on BN5 in 50% matrix achieved a high external quantum efficiency (EQE) of 3.7% and the Commission Internationale de L'Eclairage (CIE) coordinates of (0.160, 0.081) which is very close to the National Television Standards Committee's (NTSC of USA) pure blue standard. Meanwhile, the non-doped device based on BN5 demonstrated a much higher EQE of 4.5%. Neat BN6-based device presented a pure monomer emission (λ peak = 420 nm) with an extremely high EQE of 5.1% and a satisfactory CIE coordinate of (0.171, 0.076). Such values are the best ever reported for 420 nm EL emission with an un-doped layer. We attributed the enhanced performance of deep blue monomer light-emitting diodes to tert-butyl groups of BNs due to a reduction of intermolecular interaction, especially the tert-butyl substituents on the molecular backbone of BN6 play a major role in inhibiting dimer and crystallization-induced emission. Image 1 • Two novel tert-butyl modified naphthyl derivates were designed, synthesized, and characterized for deep blue emission. • Neat BN6-based device displayed an extremely high EQE of 5.1% and a satisfactory CIE coordinate of (0.171, 0.076). • Tert-butyl groups of BNs decreased intermolecular interaction, suppressed dimer and stabilized monomer emission. [ABSTRACT FROM AUTHOR]