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Comprehensive Summary: Localized surface plasmon resonance has been demonstrated to provide effective photophysical enhancement mechanisms in plasmonic photocatalysis. However, it remains highly challenging for distinct mechanisms to function in synergy for a collective gain in catalysis due to the lack of spatiotemporal control of their effect. Herein, the anisotropic plasmon resonance nature of Au nanorods was exploited to achieve distinct functionality towards synergistic photocatalysis. Photothermal and photochemical effects were enabled by the longitudinal and transverse plasmon resonance modes, respectively, and were enhanced by partial coating of silica nanoshells and epitaxial growth of a reactor component. Resonant excitation leads to a synergistic gain in photothermal‐mediated hot carrier‐driven hydrogen evolution catalysis. Our approach provides important design principles for plasmonic photocatalysts in achieving spatiotemporal modulation of distinct photophysical enhancement mechanisms. It also effectively broadens the sunlight response range and increases the efficacy of distinct plasmonic enhancement pathways towards solar energy harvesting and conversion. [ABSTRACT FROM AUTHOR]

Reducing the driving voltage is a long‐term and important challenge in the development of light‐emitting diodes (LEDs) because the light‐emission threshold voltage cannot be below the theoretical limit of the emitter's bandgap divided by the elementary charge. Here, green perovskite nanocrystal (PeNC) LEDs are inverted that emit light at ultralow voltages (below the theoretical limit) realized by efficient Auger‐assisted energy up‐conversion at the interface of the zinc oxide nanoparticles (ZnO NPs) electron injection layer and PeNC light‐emission layers. The up‐conversion utilizes the recombination energy of the charge‐transfer excitons. After modifying the interface by plasma treatment of the ZnO NPs and by inserting an organic interlayer between the ZnO NPs and PeNCs, the device performance is dramatically improved from that of the unmodified PeNC LED. The threshold voltage at which the emission spectrum can be observed is 1.55 V, substantially lower than 2.34 V (the PeNC emitter's bandgap divided by the elementary charge). Moreover, after mixing an organic aromatic semiconductor compound in the PeNC light‐emission layer, the carrier balance is regulated and the threshold voltage is further reduced to 1.30 V. [ABSTRACT FROM AUTHOR]

As a new organic photocatalyst, polymeric carbon nitride (CN) has shown good application potential in the field of photoelectrochemistry due to its unique physical and chemical properties, but its application has been seriously hindered due to its inherent characteristics such as the difficulty in charge separation. In this study, FeOOH modified CN photoanode (CN−Fe) was constructed to investigate the effect of the cocatalyst on the charge injection capacity of organic semiconductor photoelectrodes. The experimental results demonstrate significant improvement in the charge injection efficiency of the photoanode due to the introduction of FeOOH cocatalyst, leading to enhanced photoelectrochemical performance with approximately 2.4 times increase in photocurrent density. By thoroughly investigating the mechanism behind the loading of FeOOH on the polymeric carbon nitride photoanode, we gained profound insights into the behavior of charge carriers and reaction kinetics during the photoelectrocatalytic process. [ABSTRACT FROM AUTHOR]

Leveraging bright and stable carbon dots (CDs) for blue light‐emitting diodes (LEDs) is a prospective but challenging topic. Aggregation‐caused quenching (ACQ) of CDs and device engineering of CDs‐LEDs are two issues. Here, blue CDs with quantum yield of 59.75% are synthesized. Hydrogen bonds increase rigidity and facilitate luminescence, while polymer chains increase spatial resistance and resist ACQ. Then, solution‐processed blue CDs‐LEDs are assembled by blending CDs into poly(N‐vinylcarbazole) (PVK) as light‐emitting layer (EML). Furthermore, several other materials are also employed as the second host to reduce injection barrier, facilitate carriers' transport, and balance carriers' distribution. In particular, the blue CDs‐LED based on the co‐host system of PVK and 4‐[1‐[4‐[bis(4‐methylphenyl)amino]phenyl]cyclohexyl]‐N‐(3‐methylphenyl)‐N‐(4‐methylphenyl)benzenamine (TAPC) achieves a maximum brightness up to 827.60 cd m−2. This work is a step forward for applying CDs in LEDs. [ABSTRACT FROM AUTHOR]

The paper investigates and analyzes the current–voltage characteristics of the CdO-CdTe-Mo heterostructure, which is photosensitive to visible and near infrared electromagnetic radiation, in a wide range of solar radiation illumination power with an AM1.5 spectrum. The effect of internal injection amplification of the primary photocurrent in the forward direction of the applied voltage to the heterostructure is established. This effect is explained in terms of the positive feedback mechanism when the resistance of the photosensitive region of the structure is modulated by injected charge carriers and the external applied bias voltage is redistributed between the p–n junction and the base region. The photosensitivity of the CdO-CdTe-Mo heterostructure, in the charge carrier injection mode, increases with an increase in the applied bias voltage and a decrease in the power of the incident solar radiation. This is explained by the effective modulation of the base of the structure by the injected charge carriers at low radiation powers. [ABSTRACT FROM AUTHOR]

Perovskite light‐emitting diodes (LEDs) are emerging light sources for next‐generation lighting and display technologies; however, their development is greatly plagued by difficulty in achieving yellow electroluminescence, environmental instability, and lead toxicity. Copper halide CsCu2I3 with intrinsic yellow emission emerges as a highly promising candidate for eco‐friendly LEDs, but the electroluminescent performance is limited by defect‐related nonradiative losses and inefficient charge transport/injection. To solve these issues, a hole‐transporting poly(9‐vinlycarbazole) (PVK)‐incorporated engineering into CsCu2I3 emitter is proposed. PVK with carbazole groups is permeated at the grain boundaries of CsCu2I3 films by interacting with the uncoordinated Cu+, reducing the CuCs and CuI antisite defects to increase the radiative recombination and enhancing the hole mobility to balance the charge transport/injection, resulting in substantially enhanced device performances. Eventually, the yellow LEDs exhibit an 8.5‐fold enhancement of external quantum efficiency, and the half‐lifetime reaches 14.6 h, representing the most stable yellow LEDs based on perovskite systems reported so far. [ABSTRACT FROM AUTHOR]

Here, we demonstrate the simultaneous utilization of both the hot carriers (electrons and holes) in the photocatalytic transformation of benzylamine to N‐benzylidenebenzylamine and the scope of reaction has also been successfully demonstrated with catalytic oxidation of 4‐methoxybenzylamine. The wavelength‐dependent excitation of AuNP allows us to tune the potential energy of charge carriers relative to the redox potential of the reactants which leads to energetically favorable product formation on the nanoparticle surface. We capture the formation of reaction intermediates and products by using in situ Raman spectroscopy, complemented by NMR spectroscopy and GC‐MS. Based on the experimental substantiations, a plausible reaction mechanism has been proposed. [ABSTRACT FROM AUTHOR]

We report fluorescent deep-blue organic light emitting diodes (OLEDs) with significantly high efficiency by enhancing singlet exciton generation via triplet-triplet annihilation (TTA). Here, electron transport layers (ETL) and exciton blocking layers (EBL) with different characteristics (especially mobility) are applied to increase singlet harvesting (using TTA process) through appropriate charge carrier injection in the emissive layer. OLED with high electron mobility ETL, 1,4-bis(2-phenyl-1,10-phenanthrolin-4-yl)benzene (p-bPPhenB) and high hole mobility EBL, 9,9-dimethyl-10-(9-phenyl-9H-carbazol-3-yl)-9,10-dihydroacridine (PCzAc) exhibit relatively high external quantum efficiency of 9.18% with deep-blue color coordinates of (0.135, 0.115) at the luminance of 1000 cd/m2 and low driving voltage (4.5 V). The transient electroluminescence measurements are conducted to investigate the relation between prompt fluorescence from the initial singlet excitons and delayed fluorescence from the TTA process. This analysis shows significant enhancement in the singlet exciton generation by TTA process and charge recombination rate. Image 1 • Charge carrier injection approach for boosting singlet exciton generation via TTA in OLEDs. • Fluorescent deep-blue OLED with proper charge carrier injection exhibits highest EQE of 9.18%. • Results show linear relation between singlet exciton generation via TTA and the charge recombination rate. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • High yield of sunlight-driven H 2 O 2 production at Co@TiO 2 was observed. • Photosensitization was achieved due to a cobalt-to-titanium-charge-transfer. • The photocatalyst is active towards nonionic surfactant degradation. Abstract In this paper we propose titanium dioxide modified with cobalt(II) 2-ethylhexanoate (Co@TiO 2) as photoactive material for the efficient visible light driven production of H 2 O 2. We demonstrate that visible light activity can be achieved thanks to a photoinduced electron transfer from the excited complex towards the TiO 2 conduction band that corresponds to a cobalt-to-titanium-charge-transfer transition. H 2 O 2 is synthetized by a combination of oxygen reduction and water oxidation, that is possible thanks to the correct band position of Co@TiO 2. A mechanism of H 2 O 2 formation is suggested on the basis of experimental evidences. Reactive oxygen intermediates, together with H 2 O 2 are responsible for the photocatalytic degradation of a nonionic surfactant, methylene blue and phenol for wastewater treatments. Finally, and quite interestingly, Co@TiO 2 can be also used in a photoelectrochemical setup, where it can be adopted both as photoanode and photocatode, and the switching potential corresponds to the redox potential of the adsorbed complex Co(III)/Co(II) couple. [ABSTRACT FROM AUTHOR]

Abstract: Amorphous silicon carbide (a‐SiC:H) is a promising material for photoelectrochemical water splitting owing to its relatively small band‐gap energy and high chemical and optoelectrical stability. This work studies the interplay between charge‐carrier separation and collection, and their injection into the electrolyte, when modifying the semiconductor/electrolyte interface. By introducing an n‐doped nanocrystaline silicon oxide layer into a p‐doped/intrinsic a‐SiC:H photocathode, the photovoltage and photocurrent of the device can be significantly improved, reaching values higher than 0.8 V. This results from enhancing the internal electric field of the photocathode, reducing the Shockley–Read–Hall recombination at the crucial interfaces because of better charge‐carrier separation. In addition, the charge‐carrier injection into the electrolyte is enhanced by introducing a TiO2 protective layer owing to better band alignment at the interface. Finally, the photocurrent was further enhanced by tuning the absorber layer thickness, arriving at a thickness of 150 nm, after which the current saturates to 10 mA cm−2 at 0 V vs. the reversible hydrogen electrode in a 0.2  m aqueous potassium hydrogen phthalate (KPH) electrolyte at pH 4. [ABSTRACT FROM AUTHOR]

Abstract: Light‐emitting electrochemical cells (LEECs) are a promising low‐cost option for display and solid‐state lighting. In these devices, the interplay of mobile ions, electrons, and holes makes for rich physics that can be leveraged for high performance. One example of this interplay is in the formation and radiative decay of excitons–bound electron and hole pairs. Considerations from exciton binding and Langevin recombination suggest that a low dielectric constant (ϵ) would enhance emission. However, emission is also enhanced by the product of the bulk hole and electron concentrations, which in LEECs are enhanced by the motion of small mobile ions yielding high dielectric constants. These competing effects make it difficult to predict whether active layers with low or high dielectric constants will optimize device performance. Here, the effect of varying the dielectric constant on the performance of LEEC devices from ionic transition‐metal complexes was studied by systematically exchanging the negative counterions paired with an iridium complex emitter. Electrochemical impedance spectroscopy, constant voltage and constant current device studies, and drift‐diffusion simulations were performed. The results clarify the competing effects of Langevin bimolecular recombination and ion‐assisted injection processes occurring in LEECs. [ABSTRACT FROM AUTHOR]

The thermally-triggered n-type doping of single-walled carbon nanotubes is demonstrated using 1,1′-bis(diphenylphosphino)ferrocene, a novel n-type dopant. Through a simple thermal vacuum process, the phosphine compounds are moderately encapsulated inside single-walled carbon nanotubes. The encapsulation into SWNTs is carefully characterized using Raman/X-ray spectroscopy and transmission electron microscopy. This easy-to-handle doping with air-stable precursors for n-type SWNTs enables the large-scale fabrication of thermoelectric materials showing an excellent power factor exceeding approximately 240 μW mK−2. [ABSTRACT FROM AUTHOR]

Highly efficient charge carrier injection from electrodes is basically required for high-performance organic light-emitting diodes (OLEDs). However, the mismatch of metal work function and energy level of charge carrier transport layers inevitably introduces the injection barrier and also greatly restricts the choice of the electrode metals. Here, a planar organic heterojunction (OHJ) C70/pentacene is used as charge generator to realize the highly efficient injection of charge carriers in OLEDs, not only achieving the high efficiency but also significantly improving the stability. More importantly, the resulting devices show an electrode work function-independent efficiency property, greatly broadening the selectivity of electrode metals. Detailed studies are presented on the transport properties of electrons and holes in single-carrier devices based on C70/pentacene OHJ by current density-voltage ( J-V) measurements at various temperatures. It can be seen that Fowler-Nordheim (F-N) tunnel model can be used to well demonstrate the J-V properties, indicating that the charge injection based on OHJ is a tunnel process. The impedance measurements found that the lower lowest unoccupied molecular orbit energy level and higher electron mobility properties are very necessary for the used electron-transport materials to reduce the space charge region width, thus realizing highly efficient electron injection. [ABSTRACT FROM AUTHOR]

Light harvesting from large size of semiconductor PbS quantum dots (QDs) with a bandgap of less than 1 eV is one of the greatest challenges precluding the development of PbS QD-based solar cells because the interfacial charge transfer (CT) from such QDs to the most commonly used electron acceptor materials is very inefficient, if it occurs at all. Thus, an alternative electron-accepting unit with a new driving force for CT is urgently needed to harvest the light from large-sized PbS QDs. Here, a cationic porphyrin is utilized as a new electron acceptor unit with unique features that bring the donor-acceptor components into close molecular proximity, allowing ultrafast and efficient electron transfer for QDs of all sizes, as inferred from the drastic photoluminescence quenching and the ultrafast formation of the porphyrin anionic species. The time-resolved results clearly demonstrate the possibility of modulating the electron transfer process between PbS QDs and porphyrin moieties not only by the size quantization effect but also by the interfacial electrostatic interaction between the positively charged porphyrin and the negatively charged QDs. This approach provides a new pathway for engineering QD-based solar cells that make the best use of the diverse photons making up the Sun's broad irradiance spectrum. [ABSTRACT FROM AUTHOR]

Spatially resolved surface photovoltage spectroscopy (SRSPS) was employed to obtain direct evidence for highly anisotropic photogenerated charge separation on different facets of a single BiVO4 photocatalyst. Through the controlled synthesis of a single crystal with preferentially exposed {010} facets, highly anisotropic photogenerated hole transfer to the {011} facet of single BiVO4 crystals was observed. The surface photovoltage signal intensity on the {011} facet was 70 times stronger than that on the {010} facets. The influence of the built-in electric field in the space charge region of different facets on the anisotropic photoinduced charge transfer in a single semiconductor crystal is revealed. [ABSTRACT FROM AUTHOR]

Diketopyrrolopyrrole (DPP)-based p-conjugated copolymers with thiophene have exceptionally high electron mobilities. This paper investigates electronic properties and charge carrier mobilities of selenophene containing analogues. Two new copolymers, with alternating thiophene DPP (TDPP) and selenophene DPP (SeDPP) units, were synthesized. Two side-chains, hexyl (Hex) and triethylene glycol (TEG) were employed, yielding polymers designated as PTDPPSeDPP-Hex and PTDPPSeDPP-TEG. Selenophene systems have smaller band gaps, with concomitant enhancement of the stability of the reduced state. For both polymers, ambipolar mobilities were observed in organic fieldeffect transistors (OFET). Grazing incidence X-ray diffraction (GIXD) data indicates preferential edge-on orientation of PTDPPSeDPP-TEG, which leads to superior charge transport properties of the TEG substituted polymer, as compared to its Hex analogue. Time-dependent-density functional theory (TDDFT) calculations corroborate the decrease in the optical band gap with the inclusion of selenophene. Ambipolar charge transport is rationalized by exceptionally wide conduction bands. ASCF calculations confirm the larger electron affinity, and therefore the greater stability, of the reduced form of the selenophene-containing DPP polymer in presence of chloroform. [ABSTRACT FROM AUTHOR]

Multifunctional donor-acceptor compound 4,4′-bis(dibenzothiophene- S,S-dioxide-2-yl)triphenylamine ( DSTPA) was obtained by linking a strongly electron-withdrawing core and a strongly electron-donating core with a biphenyl bridge in linear spatial alignment. DSTPA not only has suitable HOMO and LUMO levels for easily accepting both holes and electrons, it was also demonstrated to have a high fluorescence quantum yield of 0.98 and a high triplet energy level of 2.39 eV. Versatile applications of DSTPA for bipolar transport, green fluorescent emission, and sensitizing a red phosphor were systematically investigated in a series of multi- and single-layer organic light-emitting devices. In traditional multilayer devices, it shows excellent performance both in an undoped fluorescent device (used as a green emitter and achieving maximum current and power efficiencies (CE and PE) of 12.6 cd A−1 and 9.4 Lm W−1, respectively) and in a red phosphorescent device (used as a host and achieving maximum CE and PE of 26.4 cd A−1 and 26.3 Lm W−1, respectively). Furthermore, DSTPA was also simultaneously used as an emitter, a hole transporter, and an electron transporter in a single-layer device showing CE and PE of 5.1 cd A−1 and 4.7 Lm W−1, respectively. A single-layer red phosphorescent device with efficiencies of 11.7 cd A−1 and 12.6 Lm W−1 was obtained by doping DSTPA with a red phosphor. The performances of all of the devices in this work are comparable to the best of their corresponding classes in the literature. [ABSTRACT FROM AUTHOR]

A series of triazole and pyridine hybrid molecules, with a triazole core and pyridine periphery, were designed and synthesized as an electron-transport layer (ETL) and a hole/exciton-block layer for green phosphorescent organic light-emitting diodes. Compared with the widely-used electron-transport material (ETM) of 3-(biphenyl-4-yl)-5-(4- tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole (TAZ) with a triazole core, lower-lying HOMO and LUMO energy levels were obtained with the introduction of pyridine rings onto the periphery of the molecules, giving improved electron injection and carrier confinement. Significantly reduced driving voltages were achieved in a device structure of ITO/HATCN (5 nm)/TAPC (40 nm)/CBP:8 wt % Ir(PPy)3 (10 nm)/ETL (40 nm)/LiF (1 nm)/Al (90 nm), giving a maximum power efficiency of 72.2 lm W−1 and an external quantum efficiency of 21.8 %, due to the improved electron injection and transport and thus, more balanced carrier recombination, which are much higher than those of the device based on TAZ. [ABSTRACT FROM AUTHOR]

Diketopyrrolopyrrole (DPP)-based π-conjugated copolymers with thiophene have exceptionally high electron mobilities. This paper investigates electronic properties and charge carrier mobilities of selenophene containing analogues. Two new copolymers, with alternating thiophene DPP (TDPP) and selenophene DPP (SeDPP) units, were synthesized. Two side-chains, hexyl (Hex) and triethylene glycol (TEG) were employed, yielding polymers designated as PTDPPSeDPP-Hex and PTDPPSeDPP-TEG. Selenophene systems have smaller band gaps, with concomitant enhancement of the stability of the reduced state. For both polymers, ambipolar mobilities were observed in organic fieldeffect transistors (OFET). Grazing incidence X-ray diffraction (GIXD) data indicates preferential edge-on orientation of PTDPPSeDPP-TEG, which leads to superior charge transport properties of the TEG substituted polymer, as compared to its Hex analogue. Time-dependent-density functional theory (TDDFT) calculations corroborate the decrease in the optical band gap with the inclusion of selenophene. Ambipolar charge transport is rationalized by exceptionally wide conduction bands. ASCF calculations confirm the larger electron affinity, and therefore the greater stability, of the reduced form of the selenophene-containing DPP polymer in presence of chloroform. [ABSTRACT FROM AUTHOR]

The effects of MoO thin buffer layer on charge carrier injection and extraction in inverted configuration ITO/ZnO/MEH-PPV (poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene))/MoO (0, 5 nm)/Ag hybrid solar cells are investigated by capacitance-voltage measurement under dark and light illumination conditions. The efficiency of charge carrier injection and extraction is enhanced by inserting 5 nm MoO thin layer, resulting in better device performances. Charge carrier transport of the whole device is improved and the interface energy barrier is reduced by inserting 5 nm MoO thin buffer layer. The device fill factor is increased from 54.1 % to 57.5 % after modifying 5 nm MoO. Simulations and experimental results consistently show that in the forward voltage under dark, the device with the 5 nm MoO thin layer modification generates larger value of capacitance than the device without MoO layer. While under illumination, the device with the 5 nm MoO layer generates smaller value of capacitance than the device without the 5 nm MoO layer in the bias region of reverse and before the peak position of maximum capacitance ( V). The underlying mechanism of the MoO anode buffer layer on device current density-voltage characteristics is discussed. [ABSTRACT FROM AUTHOR]

Perovskite light-emitting diodes (LEDs) are emerging light sources for next-generation lighting and display technologies; however, their development is greatly plagued by difficulty in achieving yellow electroluminescence, environmental instability, and lead toxicity. Copper halide CsCu 2 I 3 with intrinsic yellow emission emerges as a highly promising candidate for eco-friendly LEDs, but the electroluminescent performance is limited by defect-related nonradiative losses and inefficient charge transport/injection. To solve these issues, a hole-transporting poly(9-vinlycarbazole) (PVK)-incorporated engineering into CsCu 2 I 3 emitter is proposed. PVK with carbazole groups is permeated at the grain boundaries of CsCu 2 I 3 films by interacting with the uncoordinated Cu + , reducing the Cu Cs and Cu I antisite defects to increase the radiative recombination and enhancing the hole mobility to balance the charge transport/injection, resulting in substantially enhanced device performances. Eventually, the yellow LEDs exhibit an 8.5-fold enhancement of external quantum efficiency, and the half-lifetime reaches 14.6 h, representing the most stable yellow LEDs based on perovskite systems reported so far., (© 2022 The Authors. Advanced Science published by Wiley-VCH GmbH.)

Two by two: A low ‐ cost, fast, and green microwave ‐ assisted approach has been developed for the controlled synthesis of core–shell Cu2O@Cu/graphene hybrids. With the unique dual ‐ conducting system consisting of graphene support and Cu layer on the surface of the Cu2O nanoparticles, the as ‐ obtained hybrids exhibited significantly enhanced lithium ion battery performance as anode materials. [ABSTRACT FROM AUTHOR]

Abstract: In this article, we report a highly efficient bilayer OLED with a maximum luminance up to 62 000 cd/m2 and a threshold voltage of 3.8 V. The device structure is indium-tin-oxide (ITO)/N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-diphenyl-4,4′-diamine (TPD)/tris-(8-hydroxyquinoline) aluminum (Alq3)/LiF/Al. Ion beam assisted deposition (IBAD) process is used to deposit the aluminum cathode on the LiF layer. The IBAD process improves the OLED performance both by increasing the maximum luminance by a factor of 3 and by reducing the threshold voltage for light-emission. The IBAD process also enhances the microstructure and morphology of the Al layer and leads to denser and more homogeneous layers. The resulting highly-packed microstructure acts as a barrier to moisture and oxygen and inhibits their penetration into the Alq3 layer, leading to the OLED lifetime and stability increasing. In order to optimize the IBAD process parameters, prior to the OLED deposition, we have characterized aluminum films deposited on glass substrates by using atomic force microscopy and X-ray diffraction. [Copyright &y& Elsevier]

Lead sulfide colloidal quantum dots (PbS CQDs) have shown great potential in photodetectors owing to their promising optical properties, especially their strong and tunable absorption. However, the limitation of the specific detectivity ( D *) in CQD near-infrared (NIR) photodetectors remains unknown due to the ambiguous noise analysis. Therefore, a clear understanding of the noise current is critically demanded. Here, we elucidate that the noise current is the predominant factor limiting D *, and the noise is highly dependent on the trap densities in halide-passivated PbS films and the carriers injected from the Schottky contact (EDT-passivated PbS films/metal). It is found that the thickness of CQDs is proportional to their interface trap density, while it is inversely proportional to their minimal bulk trap density. A balance point can be reached at a certain thickness (136 nm) to minimize the trap density, giving rise to the improvement of D *. Utilizing thicker PbS-EDT films broadens the width of the tunneling barrier and thereby reduces the carrier injection, contributing to a further enhancement of D *. The limiting factors of D * determined in this work not only explain the physical mechanism of the influence on detection sensitivity but also give guidance to the design of high-performance CQD photodetectors.

Transport of charge carriers in organic layers plays a relevant role in the performance of electronic devices such as light-emitting diodes, solar cells, and photodetectors. The presence of energetically distributed traps severely affects the measured transport coefficient and the charge-storage features in the film. We summarize recent theoretical work on impedance spectroscopy models for space-charge limited current of a single carrier in a multiple trapping model, which describes the experimental behavior usually observed in organic layers with injected charge carriers well. Two main physical effects are obtained from the numerical and analytical treatment. First, carriers in slow traps that do not follow alternating current modulation provide an increase in the capacitance at low frequency, and second, those in fast traps remain in equilibrium with the transport state increasing the transit time. Analysis also provides a unified interpretation of models with field- or carrier-density dependence on mobility. [ABSTRACT FROM AUTHOR]

Organic field-effect transistors (OFETs) are the key elements of future low cost electronics such as radio frequency identification tags. In order to take full advantage of organic electronics, low power consumption is mandatory, requiring the use of a complementary metal oxide semiconductor (CMOS) like technique. To realize CMOS-devices p-type and n-type organic field-effect transistors on one substrate have to be provided. Here, the latest concepts to produce in a straightforward way complementary acting OFETs for CMOS-like elements are illustrated on basis of the inverter. Starting from a simple description of thin-film transistors, the basic design rules for the development of complementary OFETs are given and some realizations of CMOS-like inverters are discussed. A CMOS-like inverter based on two identical field-effect transistors disclosing almost unipolar p-type and n-type behavior is presented. [ABSTRACT FROM AUTHOR]

Abstract: The hole injection from a carbazole derivative hole transport layer into nanoparticles (r =25±15nm) of the conjugated polymer MEH-PPV was investigated by an indirect single-particle fluorescence-quenching technique. The results suggest that there is a kinetic barrier for hole injection that prevents polymer particles from being charged in the dark. This barrier can be overcome with the assistance of optical excitation of the MEH-PPV nanoparticles, achieving a thermodynamic population of injected holes at positive bias. The amount of injected holes at equilibrium is observed to depend upon the bias in a manner highly consistent with device simulations based on a continuum model. Overall, the results demonstrate that the hole injection into nano domains of conjugated polymers is a complex process depending upon molecular interfacial effects determined by device geometry and electrostatic interactions. [Copyright &y& Elsevier]

Abstract: We present a method for improving the efficiency of charge carrier injection at both cathode and anode of inverted top-emitting organic light-emitting diode (TOLED). In this method, a bottom-emitting OLED (BOLED) is first fabricated on a flexible substrate, which is then transferred as a whole to a glass substrate for the fabrication of the inverted TOLED (ITOLED). The electrode engineering that is responsible for the improvement, which is not possible in the traditional fabrication of ITOLED, is made realizable by the whole device transfer. [Copyright &y& Elsevier]

The physics of organic disordered materials is dominated by the effects of energetic disorder. We show that image forces reduce the electrostatic component of the total energetic disorder near an interface with a metal electrode. Typically, the standard deviation of energetic disorder is dramatically reduced at the first few layers of organic semiconductor molecules adjacent to the metal electrode. This means that the use of bulk disorder parameters (such as standard deviation of disorder) for description of the energetic disorder at the interface is poorly justified even in the case of identical spatial and chemical structure of the organic material at the interface and in the bulk of the transport layer. Implications for charge injection into organic semiconductors are discussed. [ABSTRACT FROM AUTHOR]

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We report on excitation laser power-dependent Raman and photoluminescence (PL) measurements on gold nanoparticles–monolayer MoS2 hybrid nanostructures. Excitation of localized surface plasmon resonances in gold nanoparticles and their subsequent non-radiative relaxation inject charge carriers (electrons) into the adjacent monolayer MoS2. Due to the non-centrosymmetric nature of monolayer MoS2, the localized electron doping induces lattice compression via inverse piezoelectric response. The resultant lattice distortion manifests as a shift as well as broadening of A 1 g (Γ) and E 2 g 1 Γ MoS2 Raman modes. A splitting of E 2 g 1 Γ mode is also observed. The PL spectra reveal power-dependent enhancement of trion feature, which again is a signature of an increasing electron doping. The observed effects are confirmed to be doping related as they are absent in monolayer MoS2 without gold nanoparticles. Our observations reveal that charge carrier injection is effectively controlled by varying the excitation laser power, which may aid in optically tuning physical response of MoS2 hybrid nanostructures and devices. [ABSTRACT FROM AUTHOR]

We report on excitation laser power-dependent Raman and photoluminescence (PL) measurements on gold nanoparticles–monolayer MoS2 hybrid nanostructures. Excitation of localized surface plasmon resonances in gold nanoparticles and their subsequent non-radiative relaxation inject charge carriers (electrons) into the adjacent monolayer MoS2. Due to the non-centrosymmetric nature of monolayer MoS2, the localized electron doping induces lattice compression via inverse piezoelectric response. The resultant lattice distortion manifests as a shift as well as broadening of A 1 g (Γ) and E 2 g 1 Γ MoS2 Raman modes. A splitting of E 2 g 1 Γ mode is also observed. The PL spectra reveal power-dependent enhancement of trion feature, which again is a signature of an increasing electron doping. The observed effects are confirmed to be doping related as they are absent in monolayer MoS2 without gold nanoparticles. Our observations reveal that charge carrier injection is effectively controlled by varying the excitation laser power, which may aid in optically tuning physical response of MoS2 hybrid nanostructures and devices. [ABSTRACT FROM AUTHOR]

Quasi‐two‐dimensional (quasi‐2D) perovskites are attracting much attention due to their impressive luminescence properties. However, the introduction of insulating bulky cations reduces the charge transport property of mixed‐dimensional perovskites and leads to lowered brightness and increased turn‐on voltage. The trade‐off between high photoluminescence quantum yield (PLQY) and electrical conductivity should be well manipulated to obtain high‐performance perovskite light‐emitting diodes (PeLEDs). Herein, quasi‐2D perovskite BA2(CsPbBr3)n‐1PbBr4‐PEO with high PLQY and excellent carrier injection efficiency is demonstrated by incorporating bulky n‐butylammonium bromide (BABr), CsPbBr3, and polyethylene oxide (PEO). BA can intercalate into the three‐dimensional perovskite framework to form a layered (quasi‐2D) perovskite structure. The ion conductive polymer PEO is used to protect quasi‐2D perovskite crystals. Additional BABr is removed by using anhydrous isopropyl alcohol as a washing agent due to its selective dissolubility. By carefully modulating the optical and electrical properties of quasi‐2D perovskite films, the maximum luminance of PeLEDs is dramatically enhanced from 191 to 33533 cd m−2, which is the brightest green quasi‐2D PeLED reported thus far, leading to an increase in external quantum efficiency from 1.81% to 8.42%. This work provides a promising route to control the optical and electrical properties of quasi‐2D perovskite films for high‐performance optoelectronic devices. A quasi‐2D perovskite with high photoluminescence quantum yield and excellent carrier injection efficiency is demonstrated by incorporating n‐butylammonium bromide, CsPbBr3 and polyethylene oxide. By modulating the optical and electrical properties of quasi‐2D perovskite films, the maximum luminance of PeLEDs is dramatically enhanced from 191 to 33 533 cd m−2, which is the brightest value yet observed for green quasi‐2D PeLEDs. [ABSTRACT FROM AUTHOR]

Solution-processed perovskite light-emitting diodes (LEDs) have attracted wide attention in the past several years. However, the overall efficiency and stability of perovskite-based LEDs remain inferior to those of organic or quantum dot LEDs. Nonradiative charge recombination and the unbalanced charge injection are two critical factors that limit the device efficiency and operational stability of perovskite LEDs. Here, we develop a strategy to modify the interface between the hole transport layer and the perovskite emissive layer with an amphiphilic conjugated polymer of poly[(9,9-bis(3'-( N, N-dimethylamino)propyl)-2,7-fluorene)- alt-2,7-(9,9-dioctylfluorene)] (PFN). We show evidences that PFN improves the quality of the perovskite film, which effectively suppresses nonradiative recombination. By further improving the charge injection balance rate, a green perovskite LED with a champion current efficiency of 45.2 cd/A, corresponding to an external quantum efficiency of 14.4%, is achieved. In addition, the device based on the PFN layer exhibits improved operational lifetime. Our work paves a facile way for the development of efficient and stable perovskite LEDs.

The stability of n ‐ type nanocarbon materials in air has yet to be realized for practical applications in organic thermoelectrics. In this work, n ‐ type carbon nanotubes stabilized by the encapsulation of air ‐ stable, redox ‐ active compounds are developed. This development readily enables the large ‐ scale fabrication of thermoelectric materials showing an excellent power factor exceeding approximately 240   μW mK−2 at raised temperatures. More information can be found in the Full Paper by Yoshiyuki Nonoguchi, Tsuyoshi Kawai et al. on page   2423 in Issue 17, 2016 (DOI: 10.1002/asia.201600810). [ABSTRACT FROM AUTHOR]

The interfacial electrostatic interaction between the positively‐charged porphyrin and the negatively‐charged quantum dot (QD) surface provides an additional driving force for efficient charge transfer (CT). On page 7435, O.F. Mohammed and co‐workers show the occurrence of an ultrafast CT from small bandgap (>1 eV) and large bandgap (<1 eV) PbS QDs to a molecular acceptor, reaching beyond the previously reported cut‐off CT bandgaps for PbS QDs. [ABSTRACT FROM AUTHOR]

Dye-sensitized solar cells (DSSCs) were built to probe the effect of the number of cyanocinnamic acid anchoring groups on the ring periphery of phenothiazine dyes. Two kinds of dyes, one with substitution on the N-terminal (1) and the other at the C-3 aromatic ring (2-5), have been synthesized for this purpose. Additionally, the number of cyanocinnamic acid groups have been increased to two in the case of compound 6. In the case of compounds 2-6, the N terminus was functionalized to carry methyl, 2-hydroxyethane, tris(ethylene oxide), or hexyl groups. Evidence for charge injection from the excited singlet state of phenothiazine to TiO 2 was secured from femtosecond transient absorption spectral studies, wherein an ultrafast charge injection process (k CI ≈10 10 -10 11  s -1 ) was witnessed. The DSSCs were built on nanocrystalline TiO 2 by using the traditional two-electrode method. Cell performance was better for carbon-functionalized phenothiazine dyes compared with that of nitrogen-functionalized dyes. The second cyanocinnamic group also increased the efficiency to 5.8 %., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Spatially resolved surface photovoltage spectroscopy (SRSPS) was employed to obtain direct evidence for highly anisotropic photogenerated charge separation on different facets of a single BiVO4 photocatalyst. Through the controlled synthesis of a single crystal with preferentially exposed {010} facets, highly anisotropic photogenerated hole transfer to the {011} facet of single BiVO4 crystals was observed. The surface photovoltage signal intensity on the {011} facet was 70 times stronger than that on the {010} facets. The influence of the built-in electric field in the space charge region of different facets on the anisotropic photoinduced charge transfer in a single semiconductor crystal is revealed., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)