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Efficient luminescence and interesting thermal properties of oligofluorenes provide the opportunity to investigate influences of molecular orientational distributions on characteristics of stimulated emission in organic semiconducting films. While vacuum-deposited terfluorene films exhibit preferential in-plane molecular orientation, they are reoriented and become isotropic with annealing around or above its glass transition temperature. Studies of stimulated emission (amplified spontaneous emission) show that the anisotropic terfluorene films exhibit higher gain and lower threshold than the isotropic films, due to larger confinement of the waveguided mode and larger cross section of stimulated emission. A net gain as high as 78 cm−1 (at a pump intensity of ∼30 kW/cm2) and a threshold as low as 0.7 kW/cm2 were observed. The results suggest that the gain and threshold of stimulated emission in organic semiconducting films could be substantially improved beyond the isotropic case if molecules and their transition dipole moments can be well aligned with the polarization of stimulated emission yet without causing significant loss and emission quenching.

We achieved a high efficiency UV-VIS organic photodetector (OPD) based on Poly[[4,8-bis[(2-ethylhexyl)oxy] benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl) carbonyl] thieno[3,4-b]thiophenediyl]] (PTB7) and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) as donor and acceptor respectively. The optical spectrum range of the OPD was between 300–800 nm, where over the 300–500 nm wavelength range the responsibility was better than Si-based detector. Especially at 350 nm, the responsibility was enhanced by 100%.

The structural characterization correlated to the processing control of hierarchical structure of planar heterojunction perovskite layer is still incomplete due to the limitations of conventional microscopy and X-ray diffraction. This present study performed the simultaneously grazing-incidence small-angle scattering and wide-angle scattering (GISAXS/GIWAXS) techniques to quantitatively probe the hierarchical structure of the planar heterojunction perovskite solar cells. The result is complementary to the currently microscopic study. Correlation between the crystallization behavior, crystal orientation, nano- and meso-scale internal structure and surface morphology of perovskite film as functions of various processing control parameters is reported for the first time. The structural transition from the fractal pore network to the surface fractal can be tuned by the chloride percentage. The GISAXS/GIWAXS measurement provides the comprehensive understanding of concurrent evolution of the film morphology and crystallization correlated to the high performance. The result can provide the insight into formation mechanism and rational synthesis design.

This article reports on the investigation of anisotropic optical properties of vacuum-deposited thin films of high-efficiency blue-emitting ter(9,9-diarylfluorene)s using variable-angle spectroscopic ellipsometry. Under deposition conditions typical for thin-film organic devices, both real and imaginary parts of refractive indices of vacuum-deposited ter(9,9-diarylfluorene) films exhibit rather significant uniaxial anisotropy with the optical axis along the surface normal. In particular, for the absorption associated with the π–π* transition of the terfluorene backbone, they show substantially larger in-plane extinction coefficients than the out-of-plane extinction coefficients. It is thus inferred that the vacuum-deposited ter(9,9-diarylfluorene) molecules tend to align their molecular axes and π–π* transition dipole moments along the substrate surface as observed previously in spin-coated films of alkyl-substituted polyfluorenes or oligofluorenes, even though the present ter(9,9-diarylfluorene)s have ri...

We demonstrate the fabrication of solution-processed MoOx-treated (s-MoOx) silver nanowire (AgNW) transparent conductive electrodes (TCEs) utilizing low-temperature (sub-100 °C) processes. The s-MoOx aggregates around the AgNW and forms gauze-like MoOx thin films between the mesh, which can effectively lower the sheet resistance by more than two orders of magnitude. Notably, these s-MoOx-treated AgNW TCEs exhibit a combination of several promising characteristics, such as a high and broad transmittance across a wavelength range of 400 to 1000 nm, transmission of up to 96.8%, a low sheet resistance of 29.8 ohm sq(-1), a low haze value of 0.90%, better mechanical properties against bending and adhesion tests, and preferable gap states for efficient hole injection in optoelectronic applications. By utilizing these s-MoOx-treated AgNW TCEs as the anode in ITO-free organic light emitting diodes, promising performance of 29.2 lm W(-1) and 10.3% external quantum efficiency are demonstrated. The versatile, multi-functional s-MoOx treatment presented here paves the way for the use of low-temperature, solution-processed MoOx as both a nanowire linker and a hole injection interfacial layer for future flexible optoelectronic devices.

In this study, a novel perovskite quantum dot (QD) spray-synthesis method is developed by combining traditional perovskite QD synthesis with the technique of spray pyrolysis. By utilizing this new technique, the synthesis of cubic-shaped perovskite QDs with a homogeneous size of 14 nm is demonstrated, which shows an unprecedented stable absolute photoluminescence quantum yield ≈100% in the solution and even in the solid-state neat film. The highly emissive thin films are integrated with light emission devices (LEDs) and organic light emission displays (OLEDs). The color conversion type QD-LED (ccQD-LED) hybrid devices exhibit an extremely saturated green emission, excellent external quantum efficiency of 28.1%, power efficiency of 121 lm W-1 , and extraordinary forward-direction luminescence of 8 500 000 cd m-2 . The conceptual ccQD-OLED hybrid display also successfully demonstrates high-definition still images and moving pictures with a 119% National Television System Committee 1931 color gamut and 123% Digital Cinema Initiatives-P3 color gamut. These very-stable, ultra-bright perovskite QDs have the properties necessary for a variety of useful applications in optoelectronics.

Four 2-(styryl)triphenylene derivatives (TSs) were synthesized for deep-blue dopant materials. By using a pyrene-containing compound, DMPPP, as the host, the TS-doped devices exhibited significant delayed fluorescence via triplet-triplet annihilation, providing the highest quantum efficiency of 10.2% and a current efficiency of 12.3 cd A(-1).

The “all carbon” organic solar cells (OSCs) based on the homocyclic molecule tetraphenyldibenzoperiflanthene (DBP) as a donor and C60 as an acceptor were comprehensively characterized. The optimized planar-mixed heterojunction device with a DBP:C60 mixture ratio of DBP : C60 (1 : 2) exhibited a power conversion efficiency of 4.47%. To understand why DBP possesses such advantageous characteristics, the correlations of the morphology, molecular stacking, carrier dynamics and performance of DBP:fullerene-based devices have been systematically studied. First, the face-on stacked DBP molecules could enhance both the absorption of light and the charge carrier mobility. Second, DBP : C60 (1 : 2) thin films with optimized domain sizes and partially interconnected acceptor grains led to the most balanced carrier mobility and the lowest bimolecular recombination in devices. Finally, the DBP molecules were found to stack closely using grazing incidence wide-angle X-ray scattering measurements, with a π–π stacking spacing of 4.58 A, indicating an effective molecular orbital overlap in DBP. The study not only reveals the promising characteristics of DBP as a donor in OSCs but the clear correlations of the thin-film nano-morphology, molecular stacking, carrier mobility and charge recombination found here could also provide insights into the characterization methodology and optimization of the small molecule OSCs.

Highly efficient deep-blue electroluminescent devices are realized via an efficient triplet–triplet annihilation process of styrylpyrene-based emitters., In this study, we revealed a new approach for the development of new triplet–triplet annihilation (TTA) materials with highly efficient deep-blue fluorescence via the incorporation of a styrylpyrene core and an electron-donating group. The resulting deep-blue emitters (PCzSP, DFASP, and DPASP) exhibit intramolecular charge transfer emissions with remarkably high emission quantum yields. The electroluminescent devices based on these three fluorophores as dopants using CBP as a host exhibit very high device efficiencies; in particular, the DPASP-doped device reveals an extremely high EQE of 12%, reaching the limit of a TTA-based device. The EL characteristics of DPASP-doped CBP-based devices at various doping concentrations (0–5%) suggest that the dopant DPASP is responsible for the TTA-type delayed fluorescence in the device; no delayed fluorescence was observed for the device using CBP as the host emitter. Moreover, when using DMPPP with ambipolar characteristics as the host, the deep-blue DPASP-doped device also gives outstanding performance with an EQE of nearly 11% with an extremely small efficiency roll-off, which was ascribed to the excellent charge balance in the emitting layer of the EL device. The TTA process of the SP-based dopants accounts significantly for the superior efficiencies of the EL devices.

This work explores the synthesis of extended dipyrromethene dyes engineered from thiophene-linked triphenylamine modules in order to favor pronounced charge transfer within the dyes and to enable their use in solar cells. We found that these soluble dyes absorb up to 760 nm in solution and 850 nm in thin films. An effective charge transfer absorption band was found at around 460 nm. In the crystal lattice, molecules are organized in layers separated by 3.50 A with pronounced π–π stacking and S⋯S interactions. The electroactivity of the dyes indicates that electron injection in PC71BM is feasible. Bulk heterojunction solar cells based upon dyes 1 and 2 in an optimized device structure ITO/Ca/1 or 2:PC71BM/MoO3/Ag provide a power conversion efficiency of about 1.5% after thermal annealing.

In this work microcavity-capped colour-tuneable SMOSCs are evaluated. By adopting a microcavity-structured cathode with optical spacer layers of different thicknesses fabricated in a Ag/NPB/Ag structure, the transmission spectra of complete devices can be tuned over the entire visible-light region (400-750 nm). The fabricated semitransparent colour-tuneable solar cells show an average efficiency of 4.78% under 1-sun illumination.

Vacuum-sublimed inorganic cesium lead halide perovskite thin films are prepared and integrated in all-vacuum-deposited solar cells. Special care is taken to determine the stoichiometric balance of the sublimation precursors, which has great influence on the device performance. The mixed halide devices exhibit exceptional stabilized power conversion efficiency (11.8%) and promising thermal and long-term stabilities.

A series of Os(II) sensitizers (TFOS-x, in which x=1, 2, or 3) with a single 4,4'-dicarboxy-2,2'-dipyridine (H2 dcbpy) anchor and two chelating 2-pyridyl (or 2-pyrimidyl) triazolate ancillaries was successfully prepared. Single-crystal X-ray structural analysis showed that the core geometry of the Os(II) -based sensitizers consisted of one H2 dcbpy unit and two eclipsed cis-triazolate fragments; this was notably different from the Ru(II) -based counterparts, in which the azolate (both pyrazolate and triazolate) fragments are located at the mutual trans-positions. The basic properties were extensively probed by using spectroscopic and electrochemical methods as well as time-dependent density functional theory (TD-DFT) calculations. Fabrication of dye-sensitized solar cells (DSCs) was then attempted by using the I(-) /I3 (-) -based electrolyte solution. One such DSC device, which utilized TFOS-2 as the sensitizer, showed promising performance characteristics with a short-circuit current density (JSC ) of 15.7 mA cm(-2) , an open-circuit voltage of 610 mV, a fill factor of 0.63, and a power conversion efficiency of 6.08 % under AM 1.5G simulated one-sun irradiation. Importantly, adequate incident photon-to-current conversion efficiency performances were observed for all TFOS derivatives over the wide spectral region of 450 to 950 nm, showing a panchromatic light harvesting capability that extended into the near-infrared regime. Our results underlined a feasible strategy for maximizing JSC and increasing the efficiency of DSCs.

Carrier dynamics in methylammonium lead halide (CH3NH3PbI3–xClx) perovskite thin films, of differing crystal morphology, are examined as functions of temperature and excitation wavelength. At room temperature, long-lived (>nanosecond) transient absorption signals indicate negligible carrier trapping. However, in measurements of ultrafast photoluminescence excited at 400 nm, a heretofore unexplained, large amplitude (50%–60%), 45 ps decay process is observed. This feature persists for temperatures down to the orthorhombic phase transition. Varying pump photon energy reveals that the fast, band-edge photoluminescence (PL) decay only appears for excitation ≥2.38 eV (520 nm), with larger amplitudes for higher pump energies. Lower photon-energy excitation yields slow dynamics consistent with negligible carrier trapping. Further, sub-bandgap two-photon pumping yields identical PL dynamics as direct absorption, signifying sensitivity to the total deposited energy and insensitivity to interfacial effects. Together with first principles electronic structure and ab initio molecular dynamics calculations, the results suggest the fast PL decay stems from excitation of high energy phonon modes associated with the organic sub-lattice that temporarily enhance wavefunction overlap within the inorganic component owing to atomic displacement, thereby transiently changing the PL radiative rate during thermalization. Hence, the fast PL decay relates a characteristic organic-to-inorganic sub-lattice equilibration timescale at optoelectronic-relevant excitation energies.

This study carefully examines carrier dynamics in highly efficient dye-sensitized solar cells (DSSCs) based on a series of recently developed dicarboxyterpyridine Ru(II) dyes (PRT-11-15). Comprehensive spectral response analyses, transient photovoltage and photocurrent measurements, and transient absorption techniques are exploited to investigate the effects of various functionalized terpyridines on carrier injection efficiency (η(inj)), electron diffusion length (L) and dye-regeneration efficiency (η(reg)). The resulting parameters are fully comprehended, which are then correlated with the origins of the device performance such as short circuit current density J(sc), open circuit voltage V(oc) and hence the overall conversion efficiency η in these Ru(II) based DSSCs.

Small-molecule organic solar cells with microcavity structures utilizing very thin solar-absorbing active layers are simulated and fabricated. By carefully fine-tuning the in-cell spacer layer and out-of-cell capping layer, highly efficient top-illuminated indium tin oxide-free solar cells are created on glass and flexible polyethylene terephthalate substrates with efficiencies of up to 5.5% and 5%, respectively.

A D-A-A-type molecular donor (DTDCTP) featuring electron-accepting pyrimidine and dicyanovinylene blocks has been synthesized for vacuum-deposited planar-mixed heterojunction solar cells with C(70) as the acceptor, giving a power conversion efficiency as high as 6.4%.

Carbazole-based materials adopting the nonconjugated substitution of triphenylsilyl (-SiPh(3)) and trityl (-CPh(3)) side groups are studied as high-triplet-energy, morphologically, and electrochemically stable host materials with tunable carrier-transport properties for organic blue electrophosphorescence. The developed host materials 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole (CzSi), 9-(4-tert-butylphenyl)-3,6-ditrityl-9H-carbazole (CzC), and 9-(4-tert-butylphenyl)-3-(triphenylsilyl)-6-trityl-9H-carbazole (CzCSi) all show high triplet energies of 2.97-3.02 eV, along with high glass transition temperatures of 131-163 degrees C and superior electrochemical stability. Nevertheless, the carrier-transport properties show rather significant dependence on different substitutions. Although three different host materials give similar peak electroluminescence efficiencies at low driving currents, the CzSi host, which has more suitable carrier-transport properties, renders broadened distributions of the triplet excitons in phosphorescent devices, reducing the quenching associated with triplet-triplet annihilation and giving larger resistance against efficiency roll-off at higher brightnesses.

Thin films of organic semiconductors have been subjected to extensive studies in the last two decades due to applications in photonics and optoelectronics. In this paper, we investigate wavelength tuning phenomena based on fluorene-cored oligomers (T3). We studied the optical properties of oligofluorene vacuum-deposited thin films and found that they show high optical anisotropy but become optical isotropic after annealing at a temperature around the glass-transition temperature. The results indicate the molecular reorientation in thin films after annealing. Using this property, we investigated the influence of molecular orientation on stimulated emission properties of organic thin films. Employing such properties, we have also demonstrated continuous tuning of the stimulated emission wavelength of a slab waveguide within one sample. Finally, we employed T3 thin film for laser application. We have also demonstrated the wavelength tuning of the organic laser with DFB structures.

Optical characteristics of microcavity organic light-emitting devices (OLEDs) having two mirrors are examined. Analyses show that a high-reflection back mirror and a low-loss high-reflection exit mirror are essential for such microcavity devices to obtain luminance enhancement relative to conventional noncavity devices. The capping layer in the composite mirror plays the role of enhancing reflection and reducing absorption loss, rather than enhancing transmission. In addition, by setting the normal-direction resonant wavelength around the peak wavelength of the intrinsic emission, one obtains the highest luminance enhancement along the normal direction and hardly detectable color shift with viewing angles, yet accompanied by highly directed emission and lower external quantum efficiency. On the other hand, the highest enhancement in external quantum efficiencies and the most uniform brightness distribution are obtained by setting the normal-direction resonant wavelength 20-40 nm longer than the peak wavelength of the intrinsic emission, yet with noticeable color shift over viewing angles. Due to the tradeoffs between different emission characteristics in choosing the resonant wavelength, the exact design of microcavity devices would depend on actual applications.

A low-threshold distributed feedback organic solid-state laser based on terfluorene and pumped by a pulsed Nd:YAG laser is reported. The second-order DFB grating with a period of 280 nm or 300 nm is realized by electron-beam lithography of the e-beam resist. Observations show lasing action occurring at 423 nm and 448 nm above the threshold with emission wavelength in the deep blue region.

The coherence lengths of organic light emitting diodes were measured using a Newton’s Ring apparatus. The results show that the coherence lengths are about 3~10?m depending on the spectral width of the devices.

In this paper, general discussions of the optical structures and rigorous electromagnetic modeling of OLEDs are given, and their applications in analyses and designs of various advanced OLED structures like microcavity OLEDs, tandem OLEDs, top-emitting OLEDs and techniques to enhance cd/A efficiencies have been discussed

The synthesis and properties of 3,6-bis(triphenylsilyl)carbazole as an effective host material for blue electrophosphorescence are reported. The electrochemically active C3 and C6 sites of carbazole are non-conjugated blocked with the steric, bulky and large-gap triphenylsilyls, the resulting new compound retains the large triplet energy of carbazole yet exhibits much enhanced morphological stability and electrochemical stability in comparison with previous carbazole-based host materials. Using this new host material, blue phosphorescent OLEDs having high efficiencies up to 16%, 30.6 cd/A and 26.7 lm/W are demonstrated.

Indium nitride (InN), because of its recently discovered narrow band-gap and superior electron transport properties, has emerged as a potentially important semiconductor for use in near-infrared (NIR) optoelectronics, solar cells, and high-speed electronics. The current barrier for extensive fundamental studies and widespread applications of InN is mostly related to the growth difficulty of high-quality InN heteroepitaxial films. We have recently demonstrated that high-quality InN/AlN heterostructures can be formed on Si(111) due to the existence of "magic" ratios between the lattice constants of comprising material pairs: 2:1 (Si:Si 3 N 4 ), 5:4 (AlN/Si), and 8:9 (InN:AlN). This new route of lattice matching allows the formation of commensurate interface with a common two-dimensional superlattice. For InN growth on AlN with nitrogen polarity, we found that the pseudomorphic to commensurate lattice transition occurs within the first monolayer of growth, resulting in an abrupt heterojunction at the atomic scale. At room temperature, the as-grown InN films on Si exhibit strong NIR photoluminescence with the peak energy at ~0.65 eV (wavelength at ~1.9 μm). Combined with the optical absorption measurements performed by transmission and spectroscopic ellipsometry, we confirmed that InN is a direct narrow band-gap semiconductor. Therefore, InN is a very ideal material for applications in NIR optoelectronics and solar cells, if other technological barriers (e.g., p -type doping) can also be overcome. In addition to the measurements of fundamental optical properties, a large valence band offset (3.10 eV) of type-I band alignment was also determined by photoelectron spectroscopy for the InN/AlN 8:9 commensurate heterojunction. The large band offsets and the strong polarization effects make the InN/AlN heterostructures very promising for applications in heterojunction field-effect transistors.

Fluorene-based materials, such as polyfluorenes or oligofluorenes, are conventionally well known as efficient blue emitting materials. Intriguingly, it is recently unveiled that ter(9,9-diarylfluorene)s also exhibit efficient unusual nondispersive bipolar carrier-transport characteristics and high carrier mobilities of >10 -3 cm 2 /Vs for both holes and electrons in the amorphous state. Making use of convenient substitution on C9 of fluorenes and corresponding variety in molecular structures and physical properties, in this work we systematically investigate influences of molecular structures, such as dialkyl-substitution vs. diaryl-substitution and oligomer length etc., on charge transport of oligofluorenes. Furthermore, utilizing liquid-crystalline properties of oligofluorenes with appropriate substitutions, comparative studies of carrier transport of oligofluornes in both vacuum-deposited amorphous states and aligned liquid-crystal glass states are also performed. Insights on intermolecular charge transport derived from the experimental observations and theoretical examinations are then discussed accordingly.

A bulk heterojunction organic solar cell with poly(3-hexylthiophene) (P3HT) as the donor and (6,6)-phenyl-C61-butyric acid methyl ester (PCBM) as the acceptor is deposited using blade coating on a hot plate at 80 °C with hot air of 70 °C applied from above. In contrast to the 30 min of conventional dichlorobenzene solvent annealing, the rapid-drying blade coating forms a dry film in 1 s. The fabrication throughput is substantially enhanced. The blade-coated film has a smoother surface roughness of 3.5 nm compared with 10.5 nm for solvent annealing; however, the desired phase separation in the 50 nm scale forms despite the rapid drying. A single layer solar cell exhibits power conversion efficiency of 4.1% with blade coating in chlorobenzene, which is the same as solvent annealing device. A multilayer device with carrier blocking layers fabricated entirely of the less toxic toluene also exhibits efficiency of 4.1%.

By introduction of nano-structured crystallite capping layers, the power conversion efficiency of top-illumination organic solar cells is improved from 4.2 ± 0.1% to 6.0 ± 0.2%, representing a 44% enhancement. This is caused by the increase in JSC and led by the enhancement in the local E distribution inside the active layers. Comprehensive finite-difference time domain simulation reveals two main reasons for this enhancement: (1) the nano-structured capping layers can be treated as gradient-index films that effectively increase the light entering the devices. (2) The nano-structured capping layers can also diffract the light from original normal-incident paths, hence increasing the absorption length inside the active layers.

We developed a general method based on fluorescence microscopy to characterize the interface dissolution in multi-layer organic light-emitting diodes (OLEDs) by blade coating. A sharp bi-layer edge was created before blade coating, with the bottom layer being insoluble and top layer soluble. After blade coating, fluorescence images showed that the edge of the top layer shifted when the layer dissolved completely, whereas the bottom layer's edge remained in place as a positioning mark. The dissolution depth was determined to be 15–20 nm when the emissive-layer host of 2,6-bis (3-(9H-carbazol-9-yl)phenyl) pyridine (26DCzPPy) was coated on the hole-transport layer of N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)-benzidine(NPB), which was consistent with a sudden drop in efficiency of orange OLEDs with layer thickness below 20 nm. Thus, the layer thickness of OLEDs was optimized to stay more than 20 nm for blade coating. For a two-color white OLED with the structure TCTA/26DCzPPy:PO-01-TB:FIrpic/TPBI, efficiency was 24 cd/A and 8.5 lm/W at 1000 cd/m2. For a three-color white OLED with Os(fptz)2(dhpm) added as the emitter, the efficiency was 12.3 cd/A and 3.7 lm/W at 1000 cd/m2. For a green device with the structure TCTA/26DCzPPy:Ir(mppy)3/TPBI, the efficiency was 41.9 cd/A and 23.4 lm/W at 1000 cd/m2.

The photophysical properties of a novel small molecule host containing carbazole/dibenzothiophene (CzDBS) were studied. Solution processing of CzDBS found well-balanced bipolar functionalities, high triplet bandgap, and good thin-film morphology. By using this compound as a host material, high-performance solution-processed blue and white phosphorescent organic light emitting devices were fabricated. The blue and white emitting devices showed maximum efficiencies, with 13.9% external quantum efficiency (EQE), 29.7 cd A−1 CE, 18.6 lm W−1 PE and 13.8% EQE, 29.1 cd A−1 CE, and 17.7 lm W−1 PE, respectively. In addition, through incorporation of the light-extraction structures, white-light emission with the Commission Internationale de I'Eclairage chromaticity coordinates (0.38, 0.40) and satisfactory efficiencies of 22.9% EQE, 48.4 cd A−1 CE, and 30.4 lm W−1 PE were demonstrated.

Ter(9,9-diarylfluorene) (TDF) neat film featuring oxygen sensing with advantages of fast response, reversibility and high efficiency is reported. The fast O2 fluorescence quenching process (4.0 × 1010 M−1 s−1) is unique and is mainly due to intact amorphous morphology of the TDF film, providing ample porous sites in nature so that O2 can travel therein freely. This, together with a large S1–T1 energy gap of TDF, leads to efficient O2 sensitization, i.e. the O2 induced S1–T1 intersystem crossing. The sensitivity can be further enhanced up to ∼10-fold and ∼20-fold in amplified spontaneous emission (ASE) and lasing action, respectively. The work thus demonstrated a new class of organic materials suited for high-speed, high-sensitivity oxygen sensing.

Small molecule BODIPY dyes incorporating conjugated substituents at the β sites have been synthesized. Solution processed inverted bulk heterojunction cells were fabricated from the blends of the dyes and PC(71)BM. The cells exhibited very high open-circuit voltages (>0.9 V) and a high conversion efficiency of 3.22% has been achieved.

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 ...

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A new D-π-A molecule (TPDCDTS) adopting coplanar diphenyl-substituted dithienosilole as a central π-bridge of triphenylamine (donor) and dicyanovinylene (acceptor) has been synthesized as donor material for small molecule organic solar cells (SMOSC) incorporating C(70) as an acceptor showed an appreciable power conversion efficiency of 3.82%.

We report highly efficient phosphor-sensitized solid-state light-emitting electrochemical cells (LECs) utilizing a phosphorescent cationic iridium complex [Ir(dFppy)2(SB)]+(PF6−) as the host and a fluorescent cationic dye (R6G) as the guest. Photophysical studies show that R6G retains a high photoluminescence quantum yield (PLQY) in highly polar media, revealing its suitable use as an emitting guest in an ionic host matrix. Such solid-state LECs achieve quantum efficiency (cd A−1) efficiency, and power efficiency up to 5.5% photon/electron, 19 cd A−1 and 21.3 lm W−1, respectively. The device quantum efficiency achieved is among the highest reported for fluorescent LECs and is higher than one would expect from the PLQY of the R6G fluorescent dye in the host film, thus indicating that phosphor-sensitization is useful for achieving highly efficient fluorescent LECs. Moreover, using narrow-band fluorescent emitters, such as R6G (FWHM, ∼50 nm), is effective in improving the color saturation of solid-state LECs based on cationic complexes.

We report a significant enhancement in terahertz emission from the indium nitride (InN) films grown along the a axis (a-plane InN), relative to the InN films grown along the c axis. The primary radiation mechanism of the a-plane InN film is found to be due to the acceleration of photoexcited carriers under the polarization-induced in-plane electric field perpendicular to the a axis, which effectively enhances the geometrical coupling of the radiation out of semiconductor. In addition, azimuthal angle dependence measurement shows that the p-polarized terahertz output consists of a large angularly independent component and a weak component with a distinctive fourfold rotation symmetry.

Raman studies of Mg-doped InN films with a Mg content from NMg=3.3×1019to5.5×1021cm−3 are reported. Raman and secondary ion mass spectroscopy data on the Mg content have been found to correlate well. Lattice dynamics of hexagonal InN with substitutional impurities and vacancies has been investigated in the framework of the cluster approach. Energy positions of local vibrational modes in InN have been calculated and compared with experimental findings. It is concluded that Raman spectroscopy is a good tool for quantitative characterization of Mg-doped InN.