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Light trapping is an important issue for solar cells to increase optical path length and optical absorption. In this work, a light trapping structure was realized for polymer solar cells by utilizing light diffusion ink which is conventionally used in display backlighting. The light scattering particles in the ink cause the deflection of light, and the number of these particles coated on a glass substrate determines the light transmission and scattering characteristics. It was observed that the short-circuit current density did not decrease with decreasing transmittance, but it increased to a highest value at an optimized transmittance. This behaviour is attributed to the trapping of scattered light in the photoactive layer. [ABSTRACT FROM AUTHOR]

A vertical polymer nanorod transistor was realized based on an air-stable poly[5,5′-bis(3-dodecyl-2-thienyl)-2,2′-bithiophene] with a high highest occupied molecular orbital energy level. The influence of the work function of the emitter on the performances of the space-charge-limited transistor was investigated. When MoO3/Al was used as the top emitter and indium tin oxide was used as the bottom collector, the operating voltage of 0.6 V, the on/off current ratio of 4 × 104, and the switching swing of 105 mV/decade were achieved. A low-power-consumption inverter was also demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: A hydrogel sensing film for a real-time and indicator-free detection of Zn2+ is developed by embedding a fluorescent indicator 11,16-bis(phenyl)-6,6,21,21-tetramethyl-m-benzi-6,21-porphodimethene in a hydrogel host poly(2-hydroxyethyl methacrylate). The sensing film shows high stability and selectivity to Zn2+. The sensitivity of the sensing film is increased by fabricating a micron-sized pillar array on the surface of the sensing film to increase the surface area. For Zn2+ concentrations of 10−4 and 10−3 M, the response time is 30 and 3s, respectively. [Copyright &y& Elsevier]

Abstract: A real-time and indicator-free sensor specific to nitric oxide (NO) is realized for the first time by integrating a sensing hydrogel film, a top-emitting polymer light-emitting diode (PLED), and a silicon photodetector. The top-emitting PLED is utilized to excite the sensing film specific to NO, and the photoluminescence of the sensing film is transformed into electric signal by the photodetector. The influence of the excitation light on the out-put photocurrent of the photodetector is diminished by two delicately selected organic filters based on their absorption spectra. Lead phthalocyanine is deposited on a top-emitting PLED as a filter for generating an excitation light without overlapping the emission maximum of the sensing hydrogel film. Poly(3-hexylthiophene) is placed in front of the photodetector as another filter to remove the excitation light. This sensor demonstrated a fast photocurrent response to NO with response time within 5min. [Copyright &y& Elsevier]

Abstract: The vertical mobility of a polymer film prepared on a textured substrate is enhanced from 10−5 cm2/Vs to 10−3 cm2/Vs by a slow drying process which is unattainable in planar substrate. Highly ordered structure is observed for polymer film treated with high-boiling-point solvent and slow solvent annealing. The enhanced vertical mobility enables the polymer space–charge-limited transistor (SCLT) capable of outputting current density as high as 100mA/cm2 while maintaining good current gain and on–off ratio. Such vertical transistor is able to drive high-power devices or mechanical actuator in large-area and flexible array. [Copyright &y& Elsevier]

Abstract: Newly synthesized red Ir complexes tris[2-(4-n-hexyl-phenyl)quinoline]iridium(III) and tris[(4-n-hexylphenyl)isoquinoline)]iridium(III) with long alkyl side chains are utilized to demonstrate the high efficiency multi-layer solution-processed red organic light-emitting diodes. Solubilities of these triplet emitters are high which enable them to be uniformly dispersed in the polymer host. Blade coating method is utilized to prepare organic multi-layers without mutual dissolution between different layers. 17cd/A current efficiency, 10lm/W power efficiency, and 8.8% external quantum efficiency can be achieved for the device with CsF/Al cathode. 10,000cd/m2 is reached at 10V. Similar quantum efficiency is also achieved with an electron-transport layer and LiF/Al cathode. [ABSTRACT FROM AUTHOR]

Abstract: We demonstrate a polymer non-field-effect transistor in a vertical architecture with an Al grid embedded in a polymer sandwiched between another two electrodes. The Al grid containing high density of self-assembled submicron openings is fabricated by a non-lithography method. This device modulates the space-charge-limited current of a unipolar polymer diode with the Al grid. The operating voltage of the device is as low as 4V, the on/off ratio is higher than one hundred, and the current gain is 104. The current density is higher than 1mA/cm2. [Copyright &y& Elsevier]

The introduction of biuret hydrogen-bonding sites onto chiral binaphthalene-based chromophores was investigated as a route to sub-micron-sized, vesicle-like aggregates endowed with chiroptical properties. The synthesis was conducted from the corresponding chiral 4,4′-dibromo-1,1′-bis(2-naphthol) via Suzuki–Miyaura coupling to afford luminescent chromophores whose emission spectrum could be tuned from blue to yellow-green through extension of the conjugation. For all compounds, the spontaneous formation of hollow spheres with a diameter of ca. 200–800 nm was evidenced by scanning electron microscopy, along with strong asymmetry in the circularly polarized absorption spectra. For some compounds, the emission also displayed circular polarization with values of glum = ca. 10–3 which could be increased upon aggregation. [ABSTRACT FROM AUTHOR]

This study explores the enhancement in magnetic and photoluminescence properties of Mn2+‐doped (CdSe)13 nanoclusters, significantly influenced by the introduction of paramagnetic centers through doping, facilitated by optimized precursor chemistry and precisely controlled surface ligand interactions. Using a cost‐effective and scalable synthesis approach with elemental Se and NaBH4 (Se‐NaBH4) in n‐octylamine, we tailored bonding configurations (Cd−O, Cd−N, and Cd−Se) on the surface of nanoclusters, as confirmed by EXAFS analysis. These bonding configurations allowed for tunable Mn2+‐doping with tetrahedral coordination, further stabilized by hydrogen‐bonded acetate ligands, as evidenced by 13C NMR and IR spectroscopy. Mulliken charge analysis indicates that the charge redistribution on Se2− suggests electron transfer between surface ligands and the nanocluster, contributing to spin fluctuations. These tailored configurations markedly increased the nanoclusters′ magnetic susceptibility and photoluminescence efficiency. The resulting nanoclusters demonstrated a clear concentration‐dependent response in emission lifetimes and intensities upon exposure to magnetic field effects (MFE) and spin‐spin coupling, alongside a large magnetic moment exceeding 40 μB at 180 K. These findings highlight the potential of these nanoclusters for magneto‐optical devices and spintronic applications, showcasing their tunable magnetic properties and exciton dynamics. [ABSTRACT FROM AUTHOR]

We report the construction of a polymer space-charge-limited transistor (SCLT), a solid-state version of vacuum tube triode. The SCLT achieves a high on/off ratio of 3×105 at a low operation voltage of 1.5 V by using high quality insulators both above and below the grid base electrode. Applying a greater bias to the base increases the barrier potential, and turns off the channel current, without introducing a large parasitic leakage current. Simulation result verifies the influence of base bias on channel potential distribution. The output current density is 1.7 mA/cm2 with current gain greater than 1000. [ABSTRACT FROM AUTHOR]

Vertical polymer space-charge limited transistor (SCLT) operated with an ultralow voltage is demonstrated. The influence of aging effect of the oxygen plasma treated indium tin oxide electrode on the hole injection barrier and on the transistor characteristics is investigated. By reducing the hole injection barrier, the on/off ratio as high as 104 is obtained at a collector to emitter voltage as low as -0.84 V. The low operation voltage is crucial to the development of low-power large-area polymer transistor array. Inverter characteristics are also demonstrated by connecting a SCLT with a load resistor. [ABSTRACT FROM AUTHOR]

Polymer light-emitting transistor is realized by vertically stacking a top-emitting polymer light-emitting diode on a polymer space-charge-limited transistor. The transistor modulates the current flow of the light-emitting diode by the metal-grid base voltage. The active semiconductor of the transistor is poly(3-hexylthiophene). Yellow poly(para-phenylene vinylene) derivative is used as the yellow emitting material. As the cathode is fixed at -12 V and the grid base voltage varies from 0.9 to -0.9 V the light emission is turned on and off with on luminance up to 1208 cd/m2. The current efficiency of the light-emitting transistor is 10 cd/A. [ABSTRACT FROM AUTHOR]

Circularly polarized luminescence (CPL) materials are promising candidates for future display technology. However, such highly efficient emitters suffer from the issues of difficult chiral separation and low photoluminescence quantum yield (PLQY). In this work, the chiral 4,4′‐biphenanthrene‐3,3′‐diol (BIPOL) unit was introduced into a thermally activated delayed fluorescence (TADF) framework for the first time. We presented two series of enantiomers, R/S‐o‐DCzBPNCN and R/S‐p‐DCzBPNCN, and the synthesis of enantiopure BIPOL can be prepared via normal column chromatography. Notably, o‐DCzBPNCN showed narrow singlet‐triplet gap of 0.05 eV, efficient TADF, and high PLQYs of 82 % in doped films. In addition, R/S‐o‐DCzBPNCN exhibited high luminescence dissymmetry factor (gPL) values of −1.94×10−2/+1.91×10−2 in doped films. The strategy of BIPOL introduction offers a new approach to organic emitters with stereospecific synthesis, TADF, and chiroptical properties. [ABSTRACT FROM AUTHOR]

Abstract: An efficient visible-to-infrared conversion film is made by blending CdTe quantum dots (CdTe QDs) of 12nm diameter in a polyvinylpyrrolidone 360 (PVP 360) polymer matrix cast by water solution. The solid-state photoluminescence quantum efficiency exceeds 10% with emission peak at 810nm. Strong 810 emission is obtained by combining the quantum dot film and a green polyfluorene light-emitting diode. Color filter is used to remove residual light below 780nm to make it entirely invisible. Infrared photo-detector is made by blending poly[5-(5-(2,5-bis(decyloxy)-4-methylphenyl)thiophen-2-yl)-2,3-bis(4-(2-ethylhexyloxy)phenyl)-7-(5-methylthiophen-2-yl)thieno[3,4-b]pyrazine] (PBDOTTP) with band-gap 1.2eV and (6,6)-phenyl-C61-butyric acid methyl ester (PCBM). The pixel contains one PD surrounded by four PLED on its four sides. The active areas of the five devices are all 1cm by 1cm and they are on the same plane. Infrared proximity sensor with photo-current over 300nA at 10cm object distance is achieved by detecting the reflected infrared signal. [Copyright &y& Elsevier]

Abstract: We reported a low band-gap conjugated polymer, poly[2,3-bis(4-(2-ethylhexyloxy)phenyl)-5,7-di(thiophen-2-yl)thieno[3,4-b]pyrazine] (PDTTP), was studied for the near infrared (NIR) photo-detector application. PDTTP shows intense absorption in NIR wavelength (to 1000nm) and the estimated optical and electrochemical band-gaps of PDTTP are quite small around 1.15eV and 1.08eV, respectively. The low band-gap and the extended long wavelength absorption originates from the introduction of alternating TP units when its parent polythieno[3,4-b]pyrazine shows excellent narrow band-gap properties. Therefore, the relatively low band-gap and intense absorption in long wavelength of PDTTP make itself a promising candidate for near-infrared photo-detector. The hole mobility of the PDTTP measured from the bottom contact field effect transistor is around 1.40×10−3 cm2/Vs with a on/off ratio of 2100. The photo-detector based on bulk hetero-junction PDTTP and (6,6)-phenyl-C61-butyric acid methyl ester blend (PCBM) has the incident photon-to-electron conversion efficiency 28.9% at 1000nm (−5V) and 6.2% at 1100nm (−5V). This photo-detector can be operated at a high-speed of 1MHz. The experimental result suggests the potential applications of low band-gap conjugated polymers on near-infrared photo-detectors. [Copyright &y& Elsevier]

Abstract: Solution-processed electron transport layers (ETL) have been fabricated by solution process and applied in multilayer polymer light-emitting diodes with tris[2-(p-tolyl)pyridine]iridium(III) blended in poly(vinylcarbazole) as the emissive layer. Three kinds of small molecular electron transport materials,including 2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi), 3-(4-biphenyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (TAZ), and 4,7-diphenyl-1,10-phenanthroline (BPhen), are tested and dissolved in methanol to form electron transport layers by blade coating. Such electron transport layer provides efficient electron injection and electron transport ability in the devices. The efficiency of the devices with the combination of ETL and LiF/Al cathode reaches 21.5cd/A at 10V (4050cd/m2). The efficiency of the devices without ETL are 3.5cd/A (13V) for LiF/Al cathode and 17cd/A (7V) for CsF/Al cathode at 1000cd/m2. The aggregation of the solution-processed ETL can be controlled by annealing temperature to further optimize the device performance to maximal efficiency of 53cd/A. [Copyright &y& Elsevier]

Abstract: The effect of the surface composition of a mixed self-assembled monolayer on the work function and wetting property of silver substrate are investigated with the mixtures of a fluorinated alkanethiol and a carboxyl-terminated alkanethiol of various chain lengths. The work function of silver can be tuned from 4.3 to 5.3eV by changing the mixing ratio while the wetting property can be modulated by adjust the relative chain length of the fluorinated thiol and the carboxyl-terminated thiol. Thus solution-processed poly(para phenylene vinylene)-based polymer light-emitting diode was made possible with high efficiency of 6.7cd/A and brightness of 40,000cd/m2. [ABSTRACT FROM AUTHOR]

Through the incorporation of various halogen‐substituted chiral organic cations, the effects of chiral molecules on the chiroptical properties of hybrid organic–inorganic perovskites (HOIPs) are investigated. Among them, the HOIP having a Cl‐substituted chiral cation exhibits the highest circular dichroism (CD) and circular polarized luminescence (CPL) intensities, indicating the existence of the largest rotatory strength, whereas the F‐substituted HIOP shows the weakest intensities. The observed modulation can be correlated to the varied magnetic transition dipole of HOIPs, which is sensitive to the d‐spacing between inorganic layers and the halogen–halogen interaction between organic cations and the inorganic sheets. These counteracting effects meet the optimal CD and CPL intensity with chlorine substitution, rendering the rotatory strength of HOIPs arranged in the order of (ClMBA)2PbI4>(BrMBA)2PbI4>(IMBA)2PbI4>(MBA)2PbI4>(FMBA)2PbI4. [ABSTRACT FROM AUTHOR]

Through the incorporation of various halogen‐substituted chiral organic cations, the effects of chiral molecules on the chiroptical properties of hybrid organic–inorganic perovskites (HOIPs) are investigated. Among them, the HOIP having a Cl‐substituted chiral cation exhibits the highest circular dichroism (CD) and circular polarized luminescence (CPL) intensities, indicating the existence of the largest rotatory strength, whereas the F‐substituted HIOP shows the weakest intensities. The observed modulation can be correlated to the varied magnetic transition dipole of HOIPs, which is sensitive to the d‐spacing between inorganic layers and the halogen–halogen interaction between organic cations and the inorganic sheets. These counteracting effects meet the optimal CD and CPL intensity with chlorine substitution, rendering the rotatory strength of HOIPs arranged in the order of (ClMBA)2PbI4>(BrMBA)2PbI4>(IMBA)2PbI4>(MBA)2PbI4>(FMBA)2PbI4. [ABSTRACT FROM AUTHOR]

• UV light was identified as one of the sources causing the degradation of polymer solar cells. • UV cut filters can improve the lifetime of the polymer solar cells. • Thin Ag capping layer can improve the stability. The degradation of the polymer solar cells in the outdoor condition was studied. It was found that the devices with normal structure (ITO/PEDOT:PSS/PBDTTT-EFT:PC 71 BM/ZrO x /Al) show better stability than those with inverted device structure (ITO/ZnO/PBDTTT-EFT:PC 71 BM/MoO 3 /Ag). PBDTTT-EFT is poly[4, 8-bis(5-(2-ethylhexyl) thiophen-2-yl) benzo [1,2-b;4,5-b'] dithiophene-2, 6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno [3,4-b]thiophene-) −2-carboxylate-2-6-diyl)] and PC 71 BM is [6,6]-phenyl-C71-butyric acid methyl ester. The major cause of degradation was attributed to the ultraviolet (UV) part of the sunlight. When the UV filter with cut-off wavelength of 400 nm was used to protect the device, the decay rate was improved by 50 times and the protected device retains 95% of their initial power conversion efficiency after 13 days outside. In the meanwhile, the decay of device fabricated by toluene was found 8 times faster than device by chlorobenzene. Thin 20 nm of Ag capping layer can further improve the stability. Degradation under water immersion indicates that the major effect of Ag is to protect against the residual moisture inside the encapsulation. [ABSTRACT FROM AUTHOR]

A continuous roll-to-roll compatible blade-coating method for multi-layers of general organic semiconductors is developed. Dissolution of the underlying film during coating is prevented by simultaneously applying heating from the bottom and gentle hot wind from the top. The solvent is immediately expelled and reflow inhibited. This method succeeds for polymers and small molecules. Uniformity is within 10% for 5 cm by 5 cm area with a mean value of tens of nanometers for both organic light-emitting diode (OLED) and solar cell structure with little material waste. For phosphorescent OLED 25 cd/A is achieved for green, 15 cd/A for orange, and 8 cd/A for blue. For fluorescent OLED 4.3 cd/A is achieved for blue, 9 cd/A for orange, and 6.9 cd/A for white. For OLED with 2 cm by 3 cm active area, the luminance variation is within 10%. Power conversion efficiency of 4.1% is achieved for polymer solar cell, similar to spin coating using the same materials. Very-low-cost and high-throughput fabrication of efficient organic devices is realized by the continuous blade-only method. [ABSTRACT FROM AUTHOR]

The microscopic states and performance of organic solar cell are investigated theoretically to explore the effect of the carrier mobility. With Ohmic contacts between the semiconductor and the metal electrodes there are two origins of carriers in the semiconductor: the photocarriers generated by photon absorption and the dark carriers diffused from the electrodes. The power efficiency of the solar cell is limited by the recombination of a carrier with either the photocarrier or a dark carrier. Near the short-circuit condition the photocarrier recombination in the semiconductor bulk decreases as the mobility increases. Near the open-circuit condition the dark carrier recombination increases with the mobility. These two opposite effects balance with one another, resulting in an optimal mobility about 10-2 cm2/V s which gives the highest power conversion efficiency. The balance of the electron and hole mobilities are not necessary to maintain the optimal efficiency also because of the balance of the photocarrier and dark carrier recombination. The efficiency remains about the same as one carrier mobility is fixed at 10-2 cm2/V s while the other one varies from 10-1 to 10-3 cm2/V s. For solar cell with a Schottky barrier between the semiconductor and the metal electrode there is no dark carrier recombination. The efficiency therefore always increases with the mobility. [ABSTRACT FROM AUTHOR]

In this paper, we present spectroscopic ellipsometry measurements of (MA0.13FA0.87)PbI3 single crystals assessed at photon energies of 0.73–6.42 eV and at temperatures between 4.4 and 400 K. At room temperature, the refractive index was dispersed as a function of frequency, which is typical of a semiconductor. The absorption spectrum exhibited several electronic transitions. We estimated a room temperature direct band gap of 1.66 ± 0.02 eV and exciton binding energy of 40 meV. With decreasing temperature, the refractive index increased. The room-temperature thermo-optic coefficients were −1.7 × 10−4 and −2.5 × 10−4 K−1 at wavelength of 600 and 1200 nm. The exciton peak position and bandgap energy exhibited a redshift, which was attributed to a reverse ordering of the band structures. Additionally, an anomaly in exciton peak position and bandgap occurred at approximately 100–200 K due to the structural phase transition. This phenomenon was associated with the coexistence of MA/FA-disordered and MA/FA-ordered domains. Our results provide a foundation for the technological development of lead halide perovskites-based photonic devices at various temperatures. [ABSTRACT FROM AUTHOR]

The instability of the organic light‐emitting diodes (OLEDs) during operation can be attributed to the existence of point defects on the organic layers. In this work, the effect of mixed‐host emissive layer and the thermal annealing treatment were investigated to eliminate defects and to boost the device performance. The mixed‐host system includes 4,4′,4′′‐tri (9‐carbazoyl) triphenylamine (TCTA) and 2,7‐bis(diphenylphosphoryl)‐9, 9′‐spirobi[fluorene] (SPPO13). The mixed‐host emissive layer with thermal annealing treatment showed low roughness and few pinholes, and the devices fabricated from this emissive layer exhibited high efficiencies, high stabilities, and long lifetimes. The red and orange‐red OLEDs exhibited efficiencies of 13.9 cd/A and 24.35 cd/A, respectively. The longest half‐lifetime (L0=500 cd/m2) of the red and orange‐red OLEDs were 158 h and 180 h, respectively. Efforts were made to solve problems in large‐area coating and to reduce the number of defects on in organic layer. Large‐active‐area (active area=3 cm×4 cm) red phosphorescent OLEDs (PhOLEDs) devices were realized with very high current efficiency up to 9 cd/A. [ABSTRACT FROM AUTHOR]

Four new solution-processable triethylsilylethynyl anthradithiophene-( TESADT ) based organic semiconductors, end-capped with phenyl ( DP -; 1 ), thien-2-yl ( DT -; 2 ), thienothien-2-yl ( DTT -; 3 ), and perfluorophenyl ( DFP -; 4 ) groups have been synthesized, characterized, and incorporated in organic thin-film transistors (OTFTs) and organic photovoltaics (OPVs). For the fabrication of solution-processed OTFT, thin films of all four compounds have been fabricated via a solution process of solution-shearing (SS), droplet-pinned crystallization (DPC), and drop-casting (DC). Among various solution-processing methods, solution-shearing produced TFTs the highest electrical performance. Thin films of compound 1 formed via the SS method exhibited p-channel characteristics, with hole mobilities as high as ∼0.034 cm 2 V −1 s −1 . The film morphologies and microstructures of these compounds have been characterized by atomic force microscopy and X-ray diffraction to rationalize device performance trends. Furthermore, DP-TESADT ( 1 ) and DFP-TESADT ( 4 ) has been employed for the fabrication of OPVs. Especially, pseudo-bilayer polymer solar cells based on an underlayer of poly(3-hexylthiophene) (P3HT) doped with 2.4% DP-TESADT and 9.1% DFP-TESADT and an upper layer of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) achieved power conversion efficiency up to 2.1%. [ABSTRACT FROM AUTHOR]

Considerable effort has been expended on the combination of a ferromagnetic layer with a perovskite film for application in light-controlled spintronic devices. However, to achieve such combinations, gaining control over the interface quality and the interaction between the ferromagnetic and perovskite layers is crucial. Studies have observed discrete distributions of organic perovskite (methylammonium lead bromide, MAPbBr 3) films, which self-assemble into nanodiscs, on iron–palladium alloy films. To achieve uniform wetting, we proposed the insertion of an ultrathin heterointerface of an aluminum oxide or graphene layer between perovskite and metal films. Through atomic force microscopy and scanning electron microscopy, we observed that the derived MAPbBr 3 coating successfully formed a continuous and dense layer without voids, with its roughness fluctuations being within a few nanometers. Magneto-optical Kerr effect measurement for material characterization revealed that the perovskite films had a negligible capping effect on magnetism. These results provide insight into the potential technological applications of perovskite/metal heterostructures. [Display omitted] • MAPbBr 3 was uniform after inserting an ultrathin AlO x or Gr. • Surface became more hydrophilic when a Gr or AlO x layer was used. • MAPbBr 3 on AlO x and Gr has a much lower grain size than that on FePd films. • AlO x or Gr layer protects against oxidation and interfacial diffusion. [ABSTRACT FROM AUTHOR]

During a thermal annealing process, the isomeric transformation from meridional ( mer ) into facial ( fac ) tris(8-hydroxyquinoline)-aluminum (Alq 3 ) based on the infrared absorption was observed to be nearly complete around 375 °C. Then, in a physical vapor transport process with post-annealed fac -Alq3 as source powder (at source temperature of 375 °C), the effects from various substrate temperatures ( T sub from 285 to 346 °C) on the transformation from fac -Alq 3 into mer -Alq 3 isomers re-condensed on the substrate were studied again, and an isomeric transformation occurs at T sub = 316 ± 2 °C. For T sub below 316 ± 2 °C, the re-condensed mer -Alq 3 isomers tend to aggregate to form close-packed micron-rods, which are composed of α-phase crystallites with an average coherent length L ∼ 46 nm. The photoluminescence (PL) spectra for these as-fabricated mer -Alq 3 films show typical green emission. However, for T sub above 316 ± 2 °C, the adsorbed fac -Alq 3 molecules on the substrate preserve their corresponding isomeric structure from the post-annealed fac -Alq 3 source and self-organize into flexible submicron-fibers. These samples are dominated by δ-phase crystallites with L ∼ 57 nm. The PL spectra for these as-fabricated fac -Alq 3 films do emit blue luminescence. Besides, Raman scattering for these mer -Alq 3 and fac -Alq 3 molecules are also compared. [ABSTRACT FROM AUTHOR]

The goal of this research is to synthesize the hyperbranched polythiophene derivatives ( P1 and P4 ) containing tetrachloroperylene bisimide as bridging moiety for investigation of thermal, electrochemical, and opto-electrical properties of these derivatives. The polymers ( P2 and P3 ) containing soft alkyl spacer as bridging moiety and linear poly(3-hexylthiophene) (P3HT) were also synthesized for comparison in this study. Polymers with high regioregularity were synthesized via the Universal Grignard metathesis polymerization. The GPC results showed that molecular weights of hyperbranched polythiophenes are higher than that of P3HT. The TGA experiments revealed a first-stage weight loss at about 300 °C for all polymers; besides, polymers containing rigid tetrachloroperylene bisimide groups possess less weight loss than P3HT after heating, indicative of enhanced thermal stabilities. The UV–vis absorption maxima of hyperbranched polymers are similar to that of P3HT in film state, while their absorption shoulder bands are stronger than that of P3HT, indicating stronger interchain interaction and shorter distance between backbones by the introduction of bridge architecture. Moreover, an attenuation of fluorescent intensity was found for those hyperbranched polymers, implying reduced recombination of excitons to emit light and more opportunity for carriers to migrate to both electrodes. Electrochemical analysis showed that introducing hyperbranched structure resulted in decreasing both LUMO and HOMO levels of polymers. All polymers were used for fabrication of polymer solar cells with the configuration of ITO/PEDOT/polymer:PC 60 BM (1:2 w/w)/LiF/Al to evaluate their performance. The power conversion efficiency (PCE) of the P3HT:PC 60 BM-based device is 0.54%, while devices based on hyperbranched polymers showed PCE values in the range of 0.45–0.84%. The morphological study of polymer:PC 60 BM blend films was performed by AFM for interpretation of efficiency trend of devices. [ABSTRACT FROM AUTHOR]

Structural characterization of various emeraldine salt (ES) and emeraldine base (EB) polyaniline (PANI) powders synthesized from chemical oxidative polymerization and then via de-doping and re-doping processes is first presented. Partial crystallinity with well-separated x-ray diffraction peaks is observed in the as-prepared ES PANI powder and an amorphous characteristic is identified in the de-doped EB PANI powder. From scanning electron microscopy, both the nanostructures of the as-prepared ES and de-doped EB PANI precipitated powders possess similar morphology. This finding reveals that the de-doping process to remove the counter-ions intercalated between the as-prepared ES PANI chains makes the de-doped EB PANI pieces become soft but does not change the nanostructures significantly. Then, the electrical conductivity perpendicular to the surface of the pressed PANI disc pellets is studied. The re-doped ES PANI pellets possess less electrical conductivity than their as-prepared counterparts, which suggests that during the re-doping process the counter-ions (Cl− or ) are re-adsorbed predominantly on the surface region of the PANI nanostructures. Besides, the re-doping of larger counter-ions (with respect to Cl−) intercalated between the PANI chains increases the d-spacing of (1 0 0) planes and hence reduces the corresponding π–π inter-chain interaction. Finally, from the temperature dependence of the electrical conductivity together with the structural information, the charge carrier hopping mechanisms perpendicular to the surface of the pressed pellets corresponding to various PANI samples are compared and discussed. [ABSTRACT FROM AUTHOR]

Abstract: The low work function cathode of blade-coated organic light-emitting diode is transferred from a soft polydimethylsiloxane (PDMS) mold by lamination without vacuum. The cathode is a bilayer of polyethylene glycol (PEG) (<10nm) and Al (100nm). A sacrificial layer of polystyrene with low Mw 1500 and melting point of 120°C is inserted between the cathode and PDMS for the subsequent mold removal at 150°C by melting polystyrene. Current efficiency of 3cd/A (1.1%) and luminance of 2500cd/m2 are achieved for green polyfluorene fluorescent emitter. 25cd/A (8.2%) and 3200cd/m2 are achieved for green phosphorescent tris[2-(p-tolyl)pyridine]iridium(III) (Ir(mppy)3) emitter in polymer blend host. The efficiency is about 70% of the devices with thermally evaporated cathode. The turn-on voltage is about 5V higher. [Copyright &y& Elsevier]

Abstract: A new series of super high brightness and luminance efficient poly(2,3-diphenyl-1,4-phenylene vinylene) (DP-PPV)-based electroluminescent (EL) polymers containing methoxy or long branched alkoxy chains were synthesized via Gilch polymerization. The branched alkoxy groups were introduced to enhance solubility for blade and spin-coating processes. Monomers of DMeO-PPV and m-Ph-PPV were used to increase steric hindrance and prevent close packing of the main chain. By controlling the feeding ratio of different monomers during polymerization, DP-PPV derivatives with high molecular weight were obtained. All synthesized polymers possess high glass transition temperatures and thermal stabilities. The maximum photoluminescent emissions of the thin films are located between 544 and 547 nm. Cyclic voltammetry analysis reveals that the band gaps of these light-emitting materials are in the range of 2.75–2.84 eV. Blade coating was used to fabricate multilayer polymer light-emitting diodes. A multilayer electroluminescent device with the configuration of ITO/PEDOT:PSS/TFB/P1/TPBi/LiF/Al exhibited a very high luminescence efficiency (10.96 cd A−1). The maximum brightness of the multilayer EL device ITO/PEDOT:PSS/TFB/P3/CsF/Al reached up to 78,050 cd m−2 with a low turn-on voltage (4.0 V). For further investigation, polymer P3 was blended with DPPFBNA to achieve white light-emitting device; the multilayer devices generated a maximum brightness of 1085 cd m−2 and a luminance efficiency of 0.75 cd A−1, with CIE coordinates (0.28, 0.33) at 11 V. [Copyright &y& Elsevier]

A near-infrared proximity sensor array is achieved by integrating a polymer light-emitting diode and a polymer photodetector (PD). A green emission is converted into deep red peaked at 670 nm by the inorganic phosphor Intematix R670 with quantum efficiency of over 20%. A bandpass filter is used to select a spectral tail of phosphor luminescence with a wavelength above 700 nm. The emissive polymer is green polyfluorene. The infrared PD contains a thick film of a blend of poly(3-hexylthiophene) and (6,6)-phenyl-C61-butyric acid methyl ester up to a thickness of 8 \mu\m. Position of a moving object at a distance of 10 cm is detected in real time by the array with dynamic images displayed on the computer screen. [ABSTRACT FROM AUTHOR]

Abstract: The influence of the iridium complex solubility on the efficiency of multi-layer solution-processed organic light-emitting diode is demonstrated by synthesized orange triplet iridium complexes with the same core. The solubility of the iridium(III) bis(4-phenylthieno[3,2-c]pyridinato-N,C 2′) acetylacetonate is increased and uniform dispersion of iridium complex in polymer host poly(vinylcarbazole) is achieved by tert-butyl and n-hexyl group modification. Blade coating technique is utilized to achieve tri-layer structures with a polymer hole-transporting layer poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(N-(4-s-butylphenyl))diphenylamine)], a host–guest emissive layer, and small-molecule hole-blocking layer 1,3,5-tris(N-phenylbenzimidazol-2-yl) benzene. The efficiency as high as 20cd/A is achieved for orange-emitting device. [Copyright &y& Elsevier]

Abstract: A uniform dispersion of highly soluble phosphorescent dendrimer emitters is achieved by blending with a polymer host poly(9-vinylcarbazole) (PVK) containing N,N′-diphenyl-N,N′-(bis(3-methylphenyl)-[1,1-biphenyl]-4,4′-diamine (TPD) and 2-(4-biphen-4′-yl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD). No visible aggregation or self-quenching was observed for guest-to-host weight ratios of up to 33:67. The dendrimers contain a fac-tris(2-phenylpyridyl)iridium(III) [Ir(ppy)3] core, first generation biphenyl-based dendrons, and 2-ethylhexyloxy surface groups. The guest–host blend is used for all solution processed organic light-emitting diodes. A maximum external and current efficiency of 10.2% and 38cd/A (at 5V and a brightness of 50cd/m2), and a maximum brightness of 27,000cd/m2 (at 14.5V), were obtained when a CsF/Al cathode was used. Blade coating was used to fabricate a multi-layer structure that also contained an electron-transport layer. The device that had a LiF/Al cathode had a maximal efficiency of 40cd/A corresponding to an external quantum efficiency of 10.8% (at 5V and a brightness of 19cd/m2). The maximum brightness of the second device was 17,840cd/m2 at 14V. [Copyright &y& Elsevier]

Abstract: Efficient red light polymer light-emitting diodes are obtained by energy transfer from host and guest blend system. Two kinds of blend systems, SPB02:(10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-[1] benzopyrano [6,7,8-ij]quinolizin-11-one)(C545T):4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) and SuperYellow (SY):poly(3,3′′′-didodecylquaterthiophene) (PQT-12), are used as the active layers. C545T is a green emitter, acting as an assistant dopant to improve the energy transfer from blue SPB02 host to red DCJTB. The efficiency can achieve to 3.3 cd/A for DCJTB and 3.5 cd/A for PQT-12 system by multilayer device structure with 2,2,2′′-(1,3,5-phenylene)-tris(1-phenyl-1H-benzimidazole) (TPBi) as electron transport layer. The SuperYellow:PQT-12 device shows great luminance of 16,930cd/m2. [Copyright &y& Elsevier]

Organic semiconductors were employed as exciton modulators, blue emitters, hole-transporting materials and hosts with resonant-appropriate singlet and triplet energies for efficient and stable white organic light emitting diodes (OLEDs). Two 4,4'-bis(N -naphthyl- N -phenylamino)benzophenones were synthesized using isomeric N -naphthyl- N -phenylamines as the donors and benzophenone as the acceptor moiety. Molecular design of new compounds allowed to obtain required combination of properties, i.e. blue prompt fluorescence in solid state with singlet energies close to those of the selected blue emitter exhibiting thermally activated delayed fluorescence (TADF), low triplet energies of 2.32 and 2.45 eV which are close to those of orange TADF emitter, good charge injecting properties (ionization potentials of 5.68 and 5.79 eV), good charge transporting properties with hole mobilities exceeding 10−4 cm2 (V s)−1 and high thermal stability with five percent weight loss temperatures up to 428 °C. The blue-emitting compounds were used as exciton modulators between the known blue and orange TADF emitters for fabrication of white OLEDs exploiting spatial exciton allocation strategy. In the frame of this strategy, resonant energy transfers: NPABP emitters → blue TADF and NPABP emitters → orange TADF emitters were investigated using different device structures towards efficient white electroluminescence. About twice higher external quantum efficiency was obtained for devices with two resonant energy transfers in comparison to that of the reference devices with one resonant energy transfer proving efficiency of spatial exciton allocation strategy for white TADF OLEDs. The best quality of white electroluminescence is characterized by CIE coordinates of (0.32, 0.31), colour temperature of 4490 K and colour rendering index of 80. Similar stability of blue and orange emission bands in white electroluminescence spectra was achieved due to the separation of charge and exciton recombination zones in the device structure. [Display omitted] • Separation of hole-electron recombination zone and exciton recombination zone in OLED. • Introducing of new exciton-modulating materials for applications in white OLEDs. • By ca. twice higher external quantum efficiency was observed for devices in comparison to that of the reference devices. • Relatively stable blue emission was observed in white electroluminescence • High quality of white electroluminescence with CIE coordinates of (0.32, 0.31), colour temperature of 4490 K and colour rendering index of 80. [ABSTRACT FROM AUTHOR]

Multilayer organic light-emitting diodes (OLEDs) produced by the fully solution-processed method without the dissolution of subsequent layers are necessary to achieve cost-effective high performance devices. Although photo-cross-linkable organic molecules and orthogonal solvents are regarded as promising approaches to avoiding dissolution, fully solution-processed multilayer OLEDs do not demand their use, making it impossible to investigate them and limiting their progress. In this work, a simple technique by means of hot wind that requires only a spin coater and a heat gun and reduces the dissolution problem is developed to produce fully solution-processed multilayer OLEDs. Results show that the average current efficiency is about 18 cd/A and the external quantum efficiency is 6% for devices with areas of 0.4 × 0.4 and 1.4 × 1.4 cm2. [Display omitted] • A technique for multilayer organic light-emitting diodes was presented. • This technique requires only a spin coater and a heat gun to reduce the dissolution problem. • The average current efficiency is about 18 cd/A and the external quantum efficiency is 6% were obtained. [ABSTRACT FROM AUTHOR]

[Display omitted] • Design strategy of deep-blue TADF emitters with maximum wavelength of 413 nm. • First observation of TADF for acceptor units containing molecules. • Unique photoinduced phenomena of polymorph acceptor-based triads. • Ratiometric UV detection with high Stern-Volmer constants (up to 0.242 [µW/cm2]−1) • Colorimetric UV detection with green → blue colour switching. In contrast to many donor–acceptor type organic luminophores exhibiting thermally activated delayed fluorescence (TADF), two deep blue TADF emitters designed in this work contain only typical electron accepting moieties with different electron accepting abilities. Derivatives of benzophenone and diphenylsulfone substituted with phenothiazine-5,5-dioxide donor moieties were synthesized and studied. In addition to the TADF, green to blue emission color switching and strong fluorescence intensity enhancement by more than 60 times was detected for THF solution of the derivative of phenothiazine-5,5-dioxide and benzophenone under increase of UV excitation dose. We proved by a variety of experimental and theoretical studies that the unusual photophysical properties of the derivative of benzophenone are mainly related to the formation of different conformers. The photostimulated intensity enhancement of the compound is due to the rise of the quantity of triplet states and their further crossing to singlet states. To our knowledge, this is the first observation of a combination of photoinduced color switching and triplet-dependent emission intensity enhancement. These properties are shown to be useful for UV sensing with very low detection limits (less than 10 μW/cm2 for the toluene solution). Under gradual increase of UV excitation dose, the DMF solution demonstrated a green → blue color swishing from (0.34; 0.44) to (0.17; 0.18) of CIE coordinates that can be detected by naked eye. [ABSTRACT FROM AUTHOR]

Vacuum-free fabrication is essential to realize large-scale production of organic solar cells. Blade-coating and printing are important solution-processing techniques to realize this idea. Preparation devices on large substrates is important for mass production; however, it is not easy to handle large substrates during fabrication procedures. In this work, we demonstrate a fabrication method for all-solution vacuum-free organic solar cells on an assembled glass substrates. Small pieces of glasses were assembled into a mosaic of larger total size for device fabrication. A gap-prefilling method was also developed to realize uniform thickness distribution. For the device with blade-coated ZnO electron transport layer, blade-coated active layer, spray-coated hole transport layer and spray-coated top electrode, power conversion efficiency of 4.19% is obtained. This showed that, by combining spray and blade coating, ultimate scale of the vacuum-free fabrication of OPV on glass substrate will not be limited by the substrate size itself, and can be scaled up to multi-meter by assembling the glasses into a mosaic. A method for all-solution vacuum-free organic solar cells on an assembled glass substrates were developed. Devices fabricated by blade-coating and spray-coating with power conversion efficiency of 4.19% was obtained. Image 1 • ‧A technique for all-solution vacuum-free organic solar cells on an assembled glass substrates is presented. • ‧A gap-prefilling method was also developed to realize uniform thickness distribution. • ‧Power conversion efficiency of 4.19% is obtained for the device with blade-coated PEDOT:PSS, blade-coated active layer, spray-coated hole transport layer and spray-coated top electrode. [ABSTRACT FROM AUTHOR]

The performance of OPV module is strongly dominated by the innovating materials and state of the art processes. Herein, we present a large-area and solution-processable OPV module, which the non-fullerene based active layer and interlayers are all deposited by blade coating. The module achieved a power conversion efficiency of 9.5% under 100 mW/cm2 AM1.5G irradiation with an active area of 216 cm2 on a 30 cm by 20 cm substrate. The power output can still maintain about 92.5% of the initial performance after 610 h of light soaking under 10000 lux LED irradiation. To the best of knowledge, it is the record high efficiency by far for OPV module with an active area over a hundred square centimeters. Image 1 • OPV module with a power conversion efficiency of 9.5% is demonstrated. • The module is fabricated on a 30 cm by 20 cm substrate. • The result shows a feasibility in the fabrication of large scale modules with excellent performance. [ABSTRACT FROM AUTHOR]

• Pinhole-free perovskite films with triple cations were obtained by optimizing fabrication technique. • The best concentration of cesium was found to realize solar cells with high stability. • Reproducible average power conversion efficiency of 9.3% was observed The rapid interest of low-cost hybrid organic-inorganic lead halide perovskite solar cells (PSCs) paved the way to develop its efficiency through different fabrication techniques. The inclusion of different monovalent organic or inorganic cation and halide anion in the A-site and X-site of the perovskite structure made the material to be stable at ambient conditions. In this study, a triple cation was carefully evaluated by stressing the importance of minimal processing steps, such as spin-coating, thermal annealing, and the addition of antisolvent. For enhancing the stability of perovskite film, different concentration of cesium cation was incorporated into the perovskite film. 10% cesium cation incorporated perovskite film showed a high reflectance with flat and full surface coverage. Considering the importance of other parameters and conditions, its stability was enhanced that made the perovskite film retain its black perovskite phase for four months even after exposure to ambient air. Power conversion efficiency (PCE) of 10.90% was measured under reverse scanning for 10% cesium incorporated perovskite solar cells. This structural, thermal and environmental stability, and reproducible characteristic behavior of the 10% cesium incorporated perovskite samples were achieved because of the modified fabrication techniques which are useful for future and large-scale applications. [ABSTRACT FROM AUTHOR]

• Pinhole-free perovskite films cannot be obtained by the hot-casting technique alone. • Perovskite films with minimum pinholes can be prepared by using the hot-casting technique and incorporating the additive. • Reproducible average power conversion efficiency of 9.24 % was observed. Organic-inorganic halide perovskite solar cells have attracted considerable attention because of its high efficiency, low-cost fabrication, and flexibility. The film morphology has to be well controlled since the presence of pinholes in the perovskite films deteriorates the performance of the devices. Therefore, a variety of methods have been developed to realize high quality perovskite films and excellent device performance. In this work, hot-casting technique and additive engineering were investigated for obtaining a better film morphology. Optical microscopy, electron scanning microscopy and X-ray diffraction were used to monitor the morphology and the crystallinity of the perovskite films. We found that pinhole-free perovskite films cannot be obtained by the hot-casting technique alone. By using the hot-casting technique and incorporating the additive in the perovskite precursor, perovskite films with minimum pinholes were obtained when optimum hot-casting temperature and the amount of the additive were used. A reproducible average power conversion efficiency of 9.24 % was observed. The findings showed that the perovskite films depend not only on the usage of hot-casting technique but also through the incorporation of additives which can be used for other perovskite materials utilizing as solar cells. [ABSTRACT FROM AUTHOR]

Graphene has been used to synthesize graphene quantum dots (GQDs) via pulsed laser ablation. By depositing the synthesized GQDs on the surface of InGaP/InGaAs/Ge triple-junction solar cells, the short-circuit current, fill factor, and conversion efficiency were enhanced remarkably. As the GQD concentration is increased, the conversion efficiency in the solar cell increases accordingly. A conversion efficiency of 33.2% for InGaP/InGaAs/Ge triple-junction solar cells has been achieved at the GQD concentration of 1.2 mg/ml, corresponding to a 35% enhancement compared to the cell without GQDs. On the basis of time-resolved photoluminescence, external quantum efficiency, and work-function measurements, we suggest that the efficiency enhancement in the InGaP/InGaAs/Ge triple-junction solar cells is primarily caused by the carrier injection from GQDs to the InGaP top subcell. [ABSTRACT FROM AUTHOR]