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This paper presents a $64 \times 2$ channel stereo-audio sensing front end with parallel asynchronous event output inspired by the biological cochlea. Each binaural channel performs feature extraction by analog bandpass filtering, and the filtered signal is encoded into events via asynchronous delta modulation (ADM). The channel central frequencies $f_{0}$ are geometrically scaled across the human hearing range. Two design techniques are highlighted to achieve the high system power efficiency: source-follower-based bandpass filters (BPFs) and asynchronous delta modulation (ADM) with adaptive self-oscillating comparison. The chip was fabricated in 0.18 $\mu \text{m}$ 1P6M CMOS, and occupies an area of $10.5 \times 4.8$ mm2. The core cochlea system operating under a 0.5 V power supply consumes 55 $\mu \text{W}$ at an output rate of 100k event/s. The measured range of $f_{0}$ is from 8 Hz to 20 kHz, and the BPF quality factor ${Q}$ can be tuned from 1 to almost 40. The 1 $\sigma $ mismatch of $f_{0}$ and ${Q}$ between two ears is 3.3% and 15%, respectively, across all channels at ${Q}\approx $ 10. Reconstruction of speech input from the event output of the chip is performed to validate the information integrity in event-domain representation, and vowel discrimination is demonstrated as a simple application using histograms of the output events. This type of silicon cochlea front end targets integration with embedded event-driven processors for low-power smart audio sensing with classification capabilities, such as voice activity detection and speaker identification.

Event-driven DSPs have the advantage of activity-dependent power consumption [1], and event-driven neural networks have shown superior power efficiency in real-time recognition tasks [2]. A bio-inspired silicon cochlea [3] functionally transforms sound input into multi-frequency-channel asynchronous event output, and hence is the natural candidate for the audio sensing frontend of event-driven signal processing systems like [1] and [2]. High-quality event encoding can be implemented as level-crossing (LC) ADCs, but the circuits are area- and power-inefficient [1]. Asynchronous delta modulation, the original form of LC sampling, on the other hand can be compactly realized even in small pixels of vision sensors [4]. Traditional audio processing employs digital FFTs and BPFs after signal acquisition by high-precision ADCs. However, it has been shown in [5] that for classification tasks like voice activity detection (VAD), good accuracy can still be attained when filtering is performed using low-power analog BPFs. This paper presents a 0.5V 55µW 64×2-channel binaural silicon cochlea aiming for ultra-low-power IoE applications like event-driven VAD, sound source localization, speaker identification and primitive speech recognition. The source-follower-based BPF and the asynchronous delta modulator (ADM) with adaptive self-oscillating comparison for event encoding are highlighted for the advancement of the system power efficiency.

The synthesis of a family of differently substituted 5- and 4,4′-ethynyl-bpy PtII bisacetylide complexes (bpy = 2,2′-bipyridine) and their postfunctionalization using click chemistry is described. CuI-catalyzed azide–alkyne [3+2] cycloaddition was an efficient method to decorate the PtII complexes with a manifold of moieties in high yields. The absorption and emission properties and the electrochemical behaviour of all of the complexes have been investigated. The studied compounds emit at room temperature between 598 and 660 nm, reaching photoluminescence quantum yields of 0.33 in solution. The bright luminescent properties of the unsubstituted bpy PtII bisacetylide complex remained unaffected upon click-functionalization as the resulting triazole substituent has no significant influence on the nonradiative decay rate constant. This route opens new possibilities for to control the bulk of the complexes, their solubility, and their further extension or immobilization on macromolecules, polymers and surfaces without affecting their intrinsic properties. Two derivatives were selected as triplet emitter molecules in solution-processed polymer-based organic light-emitting devices.

Highly efficient blue electrophosphorescent organic light-emitting diodes incorporating a bipolar host, 2,7-bis(diphenylphosphoryl)-9-[4-(N,N-diphenylamino)phenyl]-9-phenylfluorene (POAPF), doped with a conventional blue triplet emitter, iridium(III) bis[(4,6-difluoro-phenyl)pyridinato-N,C 2 ]picolinate (Flrpic) are fabricated. The molecular architecture of POAPF features an electron-donating (p-type) triphenylamine group and an electron-accepting (n-type) 2,7-bis(diphenylphosphoryl)fluorene segment linked through the sp 3 -hybridized C9 position of the fluorene unit. The lack of conjugation between these p- and n-type groups endows POAPF with a triplet energy gap (E T ) of 2.75 eV, which is sufficiently high to confine the triplet excitons on the blue-emitting guest In addition, the built-in bipolar functionality facilitates both electron and hole injection. As a result, a POAPF-based device doped with 7 wt% Flrpic exhibits a very low turn-on voltage (2.5 V) and high electroluminescence efficiencies (20.6% and 36.7 lm W -1 ). Even at the practical brightnesses of 100 and 1000 cd m -2 , the efficiencies remain high (20.2%/33.8 lm W -1 and 18.8%/ 24.3 lm W -1 , respectively), making POAPF a promising material for use in low-power-consumption devices for next-generation flat-panel displays and light sources.

A series of neutral, dinuclear, luminescent rhenium(I) complexes suitable for phosphorescent organic light emitting devices (OLEDs) is reported. These compounds, of general formula [Re2(m-Cl)2(CO)6(m-1,2-diazine)], contain diazines bearing alkyl groups in one or in both the b positions. Their electrochemical and photophysical properties are presented, as well as a combined density functional and time-dependent density functional study of their geometry, relative stability and electronic structure. The complexes show intense green/yellow emissions in toluene solution and in the solid state and some of the complexes possess high emission quantum yields (f=0.18–0.22 for the derivatives with disubstituted diazines). In butyronitrile glass, at 77K, due to the charge transfer character of the lowest (emitting) excited state, strong blue shift of the emission is observed, accompanied by a strong increase in the lifetime values. The highest-performing emitting complex, containing cyclopentapyridazine as ligand, is tested in a polymer-based lightemitting device, with poly(9-vinylcarbazole) as matrix, as well as in a device obtained by vacuum sublimation of the complex in the 2,7bis(diphenylphosphine oxide)-9-(9-phenylcarbazol-3-yl)-9-phenylfluorene (PCF) matrix. This represents the first example of devices obtained with a rhenium complex which can be sublimed and is solution processable. Furthermore, the emission is the bluest ever reported for electrogenerated luminescence for rhenium complexes.

We have prepared efficient red organic light-emitting diodes (OLEDs) incorporating 2,7-bis(diphenylphosphoryl)-9-[4-(N,N-diphenylamino)phenyl]-9-phenylfluorene (POAPF) as the host material doped with the osmium phosphor Os(fptz)2(PPh2Me)2 (fptz = 3-trifluoromethyl-5-pyridyl-1,2,4-triazole). POAPF, which possesses bipolar functionalities, can facilitate both hole- and electron-injection from the charge transport layers to provide a balanced charge flux within the emission layer. The peak electroluminescence performance of the device reached as high as 19.9% and 34.5 lm/W – the highest values reported to date for a red phosphorescent OLED. In addition, we fabricated a POAPF-based white light OLED – containing red-[doped with Os(fptz)2(PPh2Me)2] and blue-emitting {doped with iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,C2′] picolinate, FIrpic} layers – that also exhibited satisfactory efficiencies (18.4% and 43.9 lm/W).

Rational design and synthesis of Ir(III) complexes (1-3) bearing two cyclometalated ligands (C--N) and one 2-(diphenylphosphino)phenolate chelate (P--O) as well as the corresponding Ir(III) derivatives (4-6) with only one (C--N) ligand and two P--O chelates are reported, where (C--NH)=phenylpyridine (ppyH), 1-phenylisoquinoline (piqH), and 4-phenylquinazoline (nazoH). Single crystal X-ray diffraction studies of 3 reveal a distorted octahedral coordination geometry, in which two nazo ligands adopt an eclipsed configuration, with the third P--O ligand located trans to the phenyl group of both nazo ligands, confirming the general skeletal pattern for 1-3. In sharp contrast, complex 4 reveals a trans-disposition for the PPh2 groups, along with the phenolate groups residing opposite the unique cyclometalated ppy ligand, which is the representative structure for 4-6. These Ir(III) complexes exhibit green-to-red photoluminescence with moderate to high quantum efficiencies in the degassed fluid state and bright emission in the solid state. For 1-6, the resolved emission spectroscopy and relaxation dynamics are well rationalized by the computational approach. OLEDs fabricated using 12 wt. % of 3 doped in CBP and with BCP as hole blocking material, give bright electroluminescence with lambda(max)=628 nm and CIE(xy) coordinates (0.65, 0.34). The turn-on voltage is 3.2 V, while the current efficiency and the power efficiency reach 11.2 cd A(-1) and 4.5 lm W(-1) at 20 mA cm(-2). The maximum efficiency reaches 14.7 cd A(-1)and 6.8 lm W(-1) upon switching to TPBI as hole blocking material. For evaluating device lifespan, the tested device incorporating CuPc as a passivation layer, 3 doped in CTP as an emitting layer, and BAlq as hole blocking material, shows a remarkably long lifetime up to 36,000 h at an initial luminance of 500 cd m(-2).

This paper describes a new polyhedral oligomeric silsesquioxane (POSS)-based blue-light electroluminescent nanoparticle, octakis[ N -(9-ethyl-9 H -carbazol-3-yl)undecanamide-11-dimethylsiloxy]silsesquioxane (POSS-C11-Cz), which contains eight carbazole chromophore arms, synthesized through the hydrosilation reaction of octakis(dimethylsiloxy)silsesquioxane with the terminal olefin Cz-C11ene. POSS-C11-Cz exhibits good thermal and electrochemical stabilities and good film-forming properties. The optical and photoluminescence spectra of POSS-C11-Cz in solution and in the solid state indicate a reduction in the degrees of aggregation and excimer formation because inter-chain interactions were prohibited by the bulky POSS core. Moreover, photoluminescence spectra of a POSS-C11-Cz (3 wt.%)/polyfluorene (97 wt.%) blend revealed that the color was stable after heating the sample at 200 °C for 5 h; in contrast, the pure polyfluorene exhibited a significant green emission at 530 nm. A triple-layer device based on this blend exhibited higher maximum brightness and luminance efficiencies relative to those of the pure polyfluorene. Thus, the organic/inorganic POSS-C11-Cz/polyfluorene blend has potential for use in polymeric light-emitting diodes because of its improved thermal and optoelectronic characteristics.

A highly efficient blue-light emitter, 2-tert-butyl-9,10-bis[4'-(diphenyl-phosphoryl)phenyl]anthracene (POAn) is synthesized, and comprises electron-deficient triphenylphosphine oxide side groups appended to the 9- and 10-positions of a 2-tert-butylanthracene core. This sophisticated anthracene compound possesses a non-coplanar configuration that results in a decreased tendency to crystallize and weaker intermolecular interactions in the solid state, leading to its pronounced morphological stability and high quantum efficiency. In addition to serving as an electron-transporting blue-light-emitting material, POAn also facilitates electron injection from the Al cathode to itself. Consequently, simple double-layer devices incorporating POAn as the emitting, electron-transporting, and -injecting material produce bright deep-blue lights having Commission Internationale de L'Eclairage coordinates of (0.15,0.07). The peak electroluminescence performance was 4.3% (2.9 cd A -1 ). For a device lacking an electron-transport layer or alkali fluoride, this device displays the best performance of any such the deep-blue Organic light-emitting diodes reported to date.

We report highly efficient blue electrophosphorescent organic light-emitting diodes (OLEDs) incorporating a bipolar host, 2,7-bis(diphenylphosphine oxide)-9-(9-phenylcarbazol-3-yl)-9-phenylfluorene (PCF), doped with iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,C2′]picolinate (FIrpic). PCF, which contains diphenylphosphine oxide groups appended onto a carbazole/fluorene hybrid, displays both electron- and hole-transporting characteristics, resulting in a low turn-on voltage (2.6 V) and greatly improved power efficiencies. In addition, the sterically hindered structure of PCF provides a compatible environment for the FIrpic dopant, alleviating concentration quenching of the phosphor at high doping levels. The device doped with 28 wt % FIrpic exhibited maximum EL efficiencies of 30.8 cd/A and 26.2 lm/W (at 121 cd/m2). Even at a high brightness of 1000 cd/m2, the efficiencies remained high (26.9 cd/A and 19.6 lm/W).

We have synthesized two fluorene-based polymeric host materials, P1 and P2, through palladium-catalyzed Suzuki couplings of monomers containing tetraphenylsilane and 3,6-disubstituted fluorene frameworks, respectively. The resultant copolymers exhibited high glass transition temperatures (Tg ≥ 215 °C) and excellent thermal stability. The conjugation lengths of polymers P1 and P2 were effectively confined through the presence of the 3,6-linkages and silane units in the polymer skeleton. The structural features endowed these copolymers with UV−violet emissions in the solid state, together with high triplet energies (ET = 2.60 eV), which were sufficiently high for P1 and P2 to serve as appropriate hosts for green-emitting phosphors. In the case of polymer P2, the incorporation of pendent carbazole groups increased the HOMO level markedly and balanced the rates of charge injection and transportation. Employing P2 doped with green-emitting fac-tris(2-phenylpyridine)iridium as the emissive layer, we fabricated ...

Electrophosphorescent copolymers have been synthesized by covalent bonding of a red-emitting osmium complex Os(bpftz), which contains two 3-trifluoromethyl-5-(4-tert-butyl-2-pyridyl)triazolate (bpftz) cyclometalated ligands, into the backbone of a bipolar polyfluorene (PF) copolymer. Employing these copolymers, a highly efficient red polymer light-emitting diode has been realised that has an external quantum efficiency of 18.0%, a maximum brightness of 38000cdm � 2 , and an emission centered at 618nm. In addition, after incorporating appropriate amounts of green-emitting benzothiadiazole (BT) and the aforementioned Os(bpftz) into the bipolar PF, an efficient white-light electroluminescent polymer is obtained that displays simultaneous blue, green, and red emissions.

We report the synthesis and characterization of a series of electrophosphorescent polymers with a polyfluorene backbone, containing a red-emitting iridium complex and carrier-transporting units as the substitutes of the C-9 position of fluorene. Different specimens and contents of the hole-transporting moieties were found to influence the electroluminescent properties of the polymers. Incorporation of a hole-transporting/electron-blocking interfacial layer and utilization of an efficient electron injection cathode led to the saturated red-emitting electrophosphorescent polymer devices with the peak luminance efficiency and power conversion efficiency of 9.3 cd A−1 and 10.5 lm W−1, respectively. The efficiencies were 8 cd A−1/8 lm W−1 and 5.9 cd A−1/4.6 lm W−1, respectively, at 100 and 1000 cd m−2.

A novel blue-emitting material, 2-tert-butyl-9,10-bis[4-(1,2,2-triphenylvinyl)phenyl]anthracene (TPVAn), which contains an anthracene core and two tetraphenylethylene end-capped groups, has been synthesized and characterized. Owing to the presence of its sterically congested terminal groups, TPVAn possesses a high glass transition temperature (155 °C) and is morphologically stable. Organic light-emitting diodes (OLEDs) utilizing TPVAn as the emitter exhibit bright saturated-blue emissions (Commission Internationale de L'Eclairage (CIE) chromaticity coordinates of x = 0.14 and y = 0.12) with efficiencies as high as 5.3 % (5.3 cd A–1)—the best performance of non-doped deep blue-emitting OLEDs reported to date. In addition, TPVAn doped with an orange fluorophore served as an authentic host for the construction of a white-light-emitting device that displayed promising electroluminescent characteristics: the maximum external quantum efficiency reached 4.9 % (13.1 cd A–1) with CIE coordinates located at (0.33, 0.39).

TFTPA (tris[4-(9-phenylfluoren-9-yl)phenyl]amine), a novel host material that contains a triphenylamine core and three 9-phenyl-9-fluorenyl peripheries, was effectively synthesized through a Friedel-Crafts-type substitution reaction. Owing to the presence of its sterically bulky 9-phenyl-9-fluorenyl groups, TFTPA exhibits a high glass transition temperature (186 °C) and is morphologically and electrochemically stable. In addition, as demonstrated from atomic force microscopy measurements, the aggregation of the triplet iridium dopant is significantly diminished in the TFTPA host, resulting in a highly efficient full-color phosphorescence. The performance of TFTPA-based devices is far superior to those of the corresponding mCP- or CBP-based devices, particularly in blue- and red-emitting electrophosphorescent device systems. The efficiency of the FIrpic-based blue-emitting device reached 12 % (26 cd A -1 ) and 18 lm W -1 at a practical brightness of 100 cd m -2 ; the Ir(piq) 2 acac-based red-emitting device exhibited an extremely low turn-on voltage (2.6 V) and a threefold enhancement in device efficiency (9.0 lm W -1 ) relative to those of reference devices based on the CBP host material.

We have synthesized a blue-light-emitting polyfluorene (PF) derivative (PF-CBZ-OXD) that presents bulky hole-transporting carbazole and electron-transporting oxadiazole pendent groups functionalized at the C-9 positions of alternating fluorene units. The results from photoluminescence and electrochemical measurements indicate that both the side chains and the PF main chain retain their own electronic characteristics in the copolymer. An electroluminescent device incorporating this polymer as the emitting layer was turned on at 4.5 V; it exhibited a stable blue emission with a maximum external quantum efficiency of 1.1%. Moreover, we doped PF-CBZ-OXD and its analogue PF-TPA-OXD with a red-light-emitting iridium phosphor for use as components of phosphorescent red-light emitters to investigate the effect of the host's HOMO energy level on the degree of charge trapping and on the electrophosphorescent efficiency. We found that spectral overlap and individual energy level matching between the host and guest were both crucial features affecting the performance of the electroluminescence devices. Atomic force microscopy measurements indicated that the dipolar nature of PF-CBZ-OXD, in contrast to the general nonpolarity of polydialkylfluorenes, provided a stabilizing environment that allowed homogeneous dispersion of the polar iridium triplet dopant. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2925–2937, 2007

We have developed efficient white-light-emitting polymers through the incorporation of low-bandgap orange-light-emitting benzoselenadiazole (BSeD) moieties into the backbone of a blue-light-emitting bipolar polyfluorene (PF) copolymer, which contains hole-transporting triphenylamine and electron-transporting oxadiazole pendent groups. By carefully controlling the concentrations of the low-energy-emitting species in the resulting copolymers, partial energy transfer from the blue-fluorescent PF backbone to the orange-fluorescent segments led to a single polymer emitting white light and exhibiting two balanced blue and orange emissions simultaneously. Efficient polymer light-emitting devices prepared using this copolymer exhibited luminance efficiencies as high as 4.1 cd/A with color coordinates (0.30, 0.36) located in the white-light region. Moreover, the color coordinates remained almost unchanged over a range of operating potentials. A mechanistic study revealed that energy transfer from the PF backbone to the low-bandgap segments, rather than charge trapping, was the main operating process involved in the electroluminescence process. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2938–2946, 2007

We have synthesized a blue-light-emitting polyfluorene derivative (PF-TPAOXD) that presents sterically hindered, dipolar pendent groups functionalized at the C-9 positions of alternating fluorene units. The incorporation of the dipolar side chains, each comprising an electron-rich triphenylamine group and an electron-deficient oxadiazole group connected through a π-conjugated bridge, endows the resultant polymer with higher highest occupied molecular orbital and lower lowest unoccupied molecular orbital energy levels, which, consequently, lead to an increase in both hole and electron affinities. An electroluminescent device incorporating this polymer as the emitting layer exhibited a stable blue emission with a maximum brightness of 2080 cd/ m 2 at 12 V and a maximum external quantum efficiency of 1.4% at a brightness of 137 cd/m 2 . Furthermore, atomic force microscopy measurements indicated that the dipolar nature of PF-TPAOXD, in contrast to the general nonpolarity of polydialkylfluorenes, provided a stabilizing environment allowing the polar organometallic triplet dopant to be dispersed homogeneously. We also fabricated an electrophosphorescent device incorporating PF-TPAOXD as the host material doped with a red-emitting osmium complex to realize red electroluminescence with Commission Internationale de l'Eclairage color coordinates of (0.66, 0.34). The resulting device exhibited a maximum external quantum efficiency of 7.3% at a brightness of 1747 cd/m 2 and a maximum brightness of 7244 cd/ m 2 .

We have developed efficient white-light-emitting polymers through the incorporation of low band gap green-light-emitting benzothiadiazole and red-light-emitting bisthiophenylbenzothiadiazole moieties into the backbone of a blue-light-emitting bipolar polyfluorene copolymer. Partial energy transfer from the blue-fluorescent polyfluorene backbone to the green- and red-fluorescent components resulted in individual emissions from the three emissive species. By carefully controlling the concentrations of the low-energy-emitting species in the resulting copolymers, the emission of white light, with contributions from each of the three primary colors, was achieved. Efficient polymer light-emitting devices prepared using these copolymers exhibited luminance efficiencies as high as 4.87 cd/A with color coordinates (0.37, 0.36) that were very close to the ideal CIE chromaticity coordinates for pure white light (0.33, 0.33). In addition, the color coordinates remained almost unchanged over a range of operating poten...

A short, efficient synthetic route has been developed for the preparation of 2,7-dibromospiro[fluorene-9,9‘-(2‘,7‘-di-n-octyloxyxanthene)], which was subsequently polymerized with the corresponding diborolane through Suzuki coupling to afford a fluorene-based homopolymer, PSFX, that contains a spiroxanthene group functionalized on the C-9 position of each fluorene repeat unit. Single-crystal X-ray diffraction analysis of the dibromo monomer revealed that the spiro-fused fluorene and xanthene moieties lie perpendicular to one another. As a consequence of the incorporation of the spiro pendant group, PSFX possesses a high glass transition temperature and good thermal stability while displaying its stable blue emission in the solid state. A light-emitting diode device prepared using PSFX as the emitting layer exhibits an efficient, stable blue emission; it has a turn-on voltage of 6 V and a maximum external quantum efficiency of 1.74% ph/el. Even when the brightness was increased up to 103 cd/m2 (ca. 11 V), ...

We have systematically examined the photoluminescence (PL) and electroluminescence (EL) behavior of blends comprising two efficient red phosphors doped, respectively, into the blue-emitting polyfluorene derivatives PF-TPA-OXD and PF-OXD. The host polymers, which contain both hole- and electron-transporting or merely electron-transporting side chains, are capable of facilitating charge injection and transport. After determining the HOMO and LUMO energy levels of these materials, we were able to match the dopant with its most suitable host to achieve the direct formation and confinement of an exciton at the dopant. This configuration also leads to a reduction in the electrical excitation of the host polymer, which in turn decreases the degree of exciton loss arising from nonradiative decay of the host triplet. Using this approach, we were able to realize the production of high-performance red-electrophosphorescent devices. For Os(fppz)-doped devices, we obtain a balanced charge recombination in conjunction with higher current and luminance when using PF-TPA-OXD as the host matrix; this device reached a maximum external quantum efficiency of 8.37% with a peak brightness of 16 720 cd/m 2 . The absence of charge-transporting pendant units, i.e., the device fabricated from poly[9,9-dioctylfluorene-2,7-diyl] (POF), led, however, to relatively poor electroluminescence characteristics (5.81% and 2144 cd/m 2 ).

A series of blue and blue-green emitters based on neutral bis- and tris-cyclometalated Ir(III) complexes with 1-benzyl-4-(2,6-difluorophenyl)-1H-1,2,3-triazole (dfptrBn) as cyclometalating ligand is reported. The bis-cyclometalated complexes of the type [Ir(dfptrBn)(2)(L(^)X)] with different ancillary ligands, L(^)X = picolinate (pic) (2) or 2-(5-(perfluorophenyl)-2H-1,2,4-triazol-3-yl)pyridine (pytrF(5)) (3), are described and their photophysical properties compared with the analogous complexes containing the archetypal 2-(2,4-difluorophenyl)pyridinato (dfppy) as cyclometaled ligand (C(^)N). Complex 2 exhibits a marked solvatochromic behavior, from 475 nm in toluene to 534 nm in formamide, due to the strong MLCT character of its emissive excited state. Complex 3 displays a true-blue emission, narrower in the visible part than FIrpic. In addition, the homoleptic complex [Ir(dfprBn)(3)] (4) and the heteroleptic compounds with mixed arylpyridine/aryltriazole ligands, [Ir(dfptrBn)(2)(C(^)N)] (C(^)N = 2-phenylpyridinato (ppy) (5) or dfppy (6)), have been synthesized and fully characterized. The facial (fac) complex fac-4 is emissive at 77 K showing a deep-blue emission, but it is not luminescent in solution at room temperature similarly to their phenylpyrazole counterparts. However, the fac isomers, fac-5 and fac-6, are highly emissive in solution and thin films, reaching emission quantum yields of 76%, with emission colors in the blue to blue-green region. The photophysical properties for all complexes have been rationalized by means of quantum-chemical calculations. In addition, we constructed electroluminescent devices, organic light-emitting diodes (OLEDs) by sublimation of fac-6, and by solution processed polymer-based devices (PLEDs) using complexes fac-5 or fac-6 as dopants.

Highly efficient red-emitting electrophosphorescent devices were fabricated by doping an iridium (Ir) complex containing trifluoromethyl (CF3)-substituted pyrimidine ligand into a conjugated bipolar polyfluorene with triphenylamine and oxadiazole as side chains. The device efficiency can be enhanced through effective exciton confinement using a layer of 1,3,5-tris(N- phenylbenzimidazol-2-yl)benzene on the cathode side and a layer of in situ polymerized tetraphenyldiamine-perfluorocyclobutane on the anode side. For a blend with 5wt% of the Ir complex, a maximum external quantum efficiency of 7.9 photon/electron % and a maximum brightness of 15800cd∕m2 are reached with Commission Internationale de L’Eclairage chromaticity coordinates of x=0.65 and y=0.34.

The Diffusion Network (DN) is a probabilistic model capable of recognising continuous-time, continuous-valued biomedical data. As the stochastic process of the DN is described by stochastic differential equations, realising the DN with analogue circuits is important to facilitate real-time simulation of a large network. This paper presents the translation of the DN into analogue Very Large Scale Integration (VLSI). With extensive simulation, the dynamic ranges of parameters and their representation in VLSI are identified. The VLSI circuits realising the stochastic unit of the DN are further designed and interconnected to form a stochastic system using noise to induce stochastic dynamics in VLSI. The circuit simulation demonstrate that the VLSI translation of the DN is satisfactory and the DN system is capable of using noise-induced stochastic dynamics to regenerate various types of continuous-time sequences.

Triplet emitters based on platinum(II) complexes have gained major attention in recent times. They can form aggregates or excimers, causing shifts in the emitted wavelengths and affecting the photoluminescence quantum yields (PLQYs). Even though this effect can be exploited for the construction of white organic light emitting diodes (WOLEDs), it is disadvantageous for applications where color purity is desirable. Terpyridine ligands and their N^C^N and N^N^C analogues have been coordinated to platinum(II), leading to neutral, mono-, or doubly charged species, some of which display bright luminescence. They can form supramolecular structures, such as nanowires, nanosheets, and polymeric mesophases, with interesting optical properties. For low-molecular-weight organoor hydrogelators, the operating mechanism of gelation has been recognized as a supramolecular effect, where the constituting fibers, usually of microscale lengths and nanoscale diameters, are formed in solution predominantly by unidirectional self-assembly. The entanglement of filaments gives a network that entraps solvent molecules within the compartments. As supramolecular gels provide fibrous aggregates with long-range order, they could be of interest in the fields of optoelectronic devices and sensors. In this context, organometallic gelators can display metal–metal interactions that influence their properties. Herein we present a straightforward one-pot synthesis of neutral, soluble platinum(II) coordination compounds bearing a dianionic tridentate terpyridine-like ligand. The coordination of an alkyl pyridine ancillary moiety to the 2,6bis(tetrazolyl)pyridine complex allowed us to enhance the solubility and thus the processability. The synthetic approach involved mild reaction conditions that involved a nonnucleophilic base and an adequate inorganic platinum(II) precursor. Moistureand oxygen exclusion were not required, and the product was easily purified by repeated precipitation (Scheme 1). The emission intensity of the complex attained a

This paper presents a novel, neuromorphic circuit that produces a continuous stream of analog random samples. The circuit encodes these samples by the temporal difference between the onset times of two subsequent voltage jumps, which mimic action potentials of biological neurons. By combining elegantly concepts from renewal theory and analog very large scale integrated technology, the circuit is principally able to sample from arbitrary distributions of positive, real random variables. Moreover, these distributions can be defined online by the circuit-user in terms of an input current time-series, without the need to reconfigure the circuit. We show results from this circuit fabricated in a CMOS 0.35- $\mu \text{m}$ technology process. Random sampling is demonstrated for the uniform, exponential, and—by means of circuit simulation—also for a more complex bimodal distribution.

We have synthesized and characterized a novel blue-emitting material, 2-tert-butyl-9,10-bis[4′-(9-p-tolyl-fluoren-9-yl)biphenyl-4-yl]anthracene (BFAn), containing an anthracene core end-capped with 9-phenyl-9-fluorenyl groups. The presence of the sterically congested fluorene groups imparts BFAn with a high thermal decomposition temperature (Td = 510 °C) and results in its forming a stable glass (Tg = 227 °C). Atomic force microscopy measurements revealed that BFAn forms high-quality amorphous films and possesses good morphological stability after annealing. Organic light-emitting diodes (OLEDs) featuring BFAn as the emitter exhibited an excellent external quantum efficiency of 5.1% (5.6 cd A−1) with Commission Internationale de L'Eclairage coordinates of (0.15, 0.12) that are very close to the National Television Standards Committee's blue standard. The power efficiency of our BFAn-based devices reached as high as 5.7 lm W−1, making them superior to other reported non-doped deep-blue OLEDs.

We have fabricated highly efficient red phosphorescent organic light-emitting diodes (PHOLEDs) incorporating a bipolar host material, 2,7-bis(phenylsulfonyl)-9-[4-(N,N-diphenylamino)phenyl]-9-phenylfluorene (SAF), doped with 7 wt% tris(1-phenylisoquinolinolato-C2,N)iridium(III) [Ir(piq)3]. Attaching the electron-donating (p-type) triphenylamine group onto the electron-accepting (n-type) 2,7-bis(phenylsulfonyl)fluorene segment (through the C9 position of the fluorene unit) imparts SAF with good morphological stability, high triplet energy gap (ET), bipolar transporting ability, and matching energy levels with adjacent carrier-transporting layers. Consequently, the SAF-based red-PHOLED exhibited a very low turn-on voltage (2.4 V) and high electroluminescence efficiencies of 15.8% and 22.0 lm W−1, superior to those of the corresponding device incorporating a conventional host material, 4,4′-N,N′-dicarbazolbiphenyl (CBP; 3.2 V, 8.5%, and 8.4 lm W−1, respectively). At a practical brightness of 1000 cd m−2, the efficiencies of the SAF-based red-PHOLED remained high (13.1%, 14.4 lm W−1).

A solution-processable bipolar material tBu-OXDTFA comprising an electron-rich triphenylamine core and electron-deficient oxadiazole/fluorene peripheries was synthesized. This dendrimer-like molecule not only possesses a high triplet energy (2.74 eV) but also exhibits excellent film-forming properties upon solution processing. We achieved highly efficient white electrophosphorescent OLEDs (22.3 cd A−1, 11.6%) through solution processing, wherein the single white emitting layer was readily formed after spin-coating a solution of blue- and red-phosphor co-dopants containing tBu-OXDTFA as the host matrix.

We report the synthesis and characterization of a novel silane–fluorene hybrid, triphenyl-(4-(9-phenyl-9H-fluoren-9-yl)phenyl)silane (TPSi-F), used as the host material for blue phosphorescent devices. TPSi-F is constructed by linking p-substituted tetraphenylsilane to the fluorene framework through a non-conjugated, sp3-hybridized carbon atom (C-9) to enhance thermal and morphological stabilities, while maintaining the much needed higher singlet and triplet energy gap. Highly efficient sky-blue phosphorescent OLEDs were obtained when employing TPSi-F as the host and iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,C2′] (FIrpic) as the guest. The maximum external quantum efficiency (max. E.Q.E.) of this device reached as high as 15% (30.6 cd A−1). Furthermore, upon switching the guest from FIrpic to a new blue phosphor FIrfpy, better blue-emitting OLEDs were produced with a max. E.Q.E. of 9.4% (15.1 cd A−1). These TPSi-F based blue phosphorescent devices show a 2-fold enhancement in device efficiency compared with reference devices based on the conventional host material 1,3-bis(9-carbazolyl)benzene (mCP).