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A series of OsII sensitizers ( TFOS- x, in which x=1, 2, or 3) with a single 4,4′-dicarboxy-2,2′-dipyridine (H2dcbpy) 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 OsII-based sensitizers consisted of one H2dcbpy unit and two eclipsed cis-triazolate fragments; this was notably different from the RuII-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. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we present vacuum-deposited bifacial transparent organic solar cells on indium-tin-oxide-coated glass substrates. Good performances and high transparencies are achieved simultaneously by employing the planar-mixed heterojunction of the organic donor 2-{[7-(5-N,N-ditolylaminothiophen-2-yl)-2,1,3-benzothiadiazol-4-yl]methylene}malononitrile (DTDCTB) and fullerenes with carefully designed resonance top electrodes. Comprehensive optical simulation is exploited to investigate the effect of the top-electrode configuration on the cell transparency and efficiency. Cells with structures designed for high transparencies were fabricated and tested. The DTDCTB:C60 device yields a high transmission of up to 66.4% at 530nm and a power conversion efficiency (PCE) of 2.11%. Moreover, the DTDCTB:C70 device demonstrates an exceptional PCE as high as 3.24% with a balanced transmission of ≈50% in the visible spectrum. Enhanced PCE values of transparent solar cells are also revealed with the use of external reflectors. Efficiency enhancements of ≈15% and ≈65% are achieved by simply attaching a reflection mirror at the cathode or anode side, respectively. [Copyright &y& Elsevier]

Abstract: 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 78cm−1 (at a pump intensity of ∼30kW/cm2) and a threshold as low as 0.7kW/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. [Copyright &y& Elsevier]

Halide perovskites have received an immense attention in the field of optoelectronics due to their outstanding photophysical properties. But so far, lead‐based halide perovskites still account for most of the research, which raises concerns due to lead toxicity. Herein, a new design strategy is proposed utilizing a super large, energetically higher singlet and triplet energy levels aromatic organic cation to incorporate into the perovskite structure, forming ultra‐stable high‐performance 2D/3D (quasi‐2D) perovskite. The judicious molecular design of connecting all the phenyl groups at their meta sites ensures the simultaneous achievement of a large molecular weight and high singlet and triplet energy levels. The resulting quasi‐2D perovskite thin films not only exhibits excellent emission properties but also, surprisingly, show long‐term waterproof‐level stability. The robustness of these perovskites is confirmed by their extraordinary emission stability upon direct water immersion and almost undetectable lead release in water. Proof‐of‐concept of a water‐resistant color conversion‐type perovskite near‐infrared (NIR) light‐emitting diode (LED) is demonstrated, showing high external quantum efficiency (EQE) and power conversion efficiency (PCE) of 20.5% and 13.3%, respectively. It is believed these results and strategy pave a new way for realizing environmentally friendly lead halide materials and devices. [ABSTRACT FROM AUTHOR]

Large-area, mixed halide, perovskites, solar cells, spray-coating Ultrasonic Spray-Coatings: Multi-Channel Pumped Ultrasonic Spray-Coating for High-Throughput and Scalable Mixed Halide Perovskite Solar Cells (Adv. Keywords: large-area; mixed halide; perovskites; solar cells; spray-coating EN large-area mixed halide perovskites solar cells spray-coating 1 1 1 03/12/21 20210309 NES 210309 In article number 2001509, Cheng-Liang Liu and coworkers demonstrate the scalable ultrasonic spray-coating method combined with ternary channel pumping of precursor solutions and vacuum-assisted thermal annealing to fabricate large-area MAPbI SB 3- I x i sb Br SB I x i sb mixed halide perovskite films of size 7 × 10 cm SP 2 sp . [Extracted from the article]

Uniform Artificial Synapses In article number 2000196, Kai‐Chiang Wu, Hao‐Wu Lin, and co‐workers demonstrate vacuum deposited halide perovskite devices that exhibit very uniform electrical synaptic characteristics. Utilizing these devices in the reservoir computing can simultaneously reduce the circuitry complexity and increase its recognition accuracy with noisy inputs. The findings promise to facilitate the utilization of highly homogeneous perovskite/metal oxide structures in high‐performance neuromorphic computing systems. [ABSTRACT FROM AUTHOR]

Vacuum Fabrication: Efficient Cesium Lead Halide Perovskite Solar Cells through Alternative Thousand-Layer Rapid Deposition (Adv. Funct. Keywords: alternative deposition; cesium; perovskite solar cells; vacuum deposition Alternative deposition, cesium, perovskite solar cells, vacuum deposition. [Extracted from the article]

The novel growth of cesium lead halide perovskite thin films, which are prepared through thousand‐layer rapid alternative deposition, is performed by developing an active perovskite film consisting of a layer‐by‐layer structure. This method is considerably more difficult to be implemented from the solution process. The obtained thin film morphology and characteristics are distinguished from that of the traditional a few layers and two‐material codeposition. These alternative deposited perovskites are integrated with vacuum‐deposited carrier‐transporting layers and electrodes, and all vacuum‐sublimed perovskite solar cells exhibit an outstanding power conversion efficiency of 13.0%. The use of these devices for environmental light energy harvesting provides a power conversion efficiency of 33.9% under fluorescent light illumination of 1000 lux. [ABSTRACT FROM AUTHOR]

Although vacuum‐deposited metal halide perovskite light‐emitting diodes (PeLEDs) have great promise for use in large‐area high‐color‐gamut displays, the efficiency of vacuum‐sublimed PeLEDs currently lags that of solution‐processed counterparts. In this study, highly efficient vacuum‐deposited PeLEDs are prepared through a process of optimizing the stoichiometric ratio of the sublimed precursors under high vacuum and incorporating ultrathin under‐ and upper‐layers for the perovskite emission layer (EML). In contrast to the situation in most vacuum‐deposited organic light‐emitting devices, the properties of these perovskite EMLs are highly influenced by the presence and nature of the upper‐ and presublimed materials, thereby allowing us to enhance the performance of the resulting devices. By eliminating Pb° formation and passivating defects in the perovskite EMLs, the PeLEDs achieve an outstanding external quantum efficiency (EQE) of 10.9% when applying a very smooth and flat geometry; it reaches an extraordinarily high value of 21.1% when integrating a light out‐coupling structure, breaking through the 10% EQE milestone of vacuum‐deposited PeLEDs. [ABSTRACT FROM AUTHOR]

Highly photoluminescent, lead‐free perovskites are of interest for displays and solid‐state light‐emitting devices. In this report, streak camera‐based time‐resolved emission and transient absorption spanning visible to deep‐ultraviolet (UV) wavelengths are utilized to study self‐trapped and free exciton dynamics in vacuum‐deposited cesium copper halide thin films of CsCu2I3 and Cs3Cu2I5. Self‐trapped exciton emission of CsCu2I3 exhibits more noticeable changes with time in the peak position and width than Cs3Cu2I5. UV‐to‐blue emission is detectable for both compositions, where free exciton emission is distinct for CsCu2I3. Transient absorption shows loss of ground‐state bleach signals at early time delays for both, and the bleach signal shifts toward higher energy as time delay increases, likely due to strains induced by the newly created self‐trapped excitons. Global analysis performed on the transient absorption results yields time constants in these materials that build an overall dynamic scheme. This work aids in building a complete picture regarding light emission in these promising materials. [ABSTRACT FROM AUTHOR]

Electromagnetic simulation and multiple light extraction concepts for solution-processed organic light-emitting diodes were explored in this report. Based on the optical simulation results, the device architecture was optimized for maximization of the light out-coupling efficiency. By utilizing a high refractive index substrate, a high light scattering electrode, and an external light extraction structure, trapped photons in the wave-guided and substrate modes were extracted effectively. The best solution-processed device exhibited a maximum external quantum efficiency of 42.9%, a current efficiency as high as 150.1 cd/A, and a power efficacy up to 125.1 lm/W. [ABSTRACT FROM AUTHOR]

Highlights: [•] Wavelength tuning of organic DFB lasers after fabrication by varying effective refractive index. [•] Vary refractive index by molecular reorientation of organic gain media at elevated temperatures. [•] Distributions of molecular orientations can be fine controlled by annealing temperatures and times. [•] Continuous tuning of the organic DFB lasing wavelengths after device fabrication is demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: Efficient inverted bulk-heterojunction (BHJ) poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester (P3HT:PCBM) organic solar cells fabricated by rapid-drying blade-coated were demonstrated. Optimized self-organization interpenetration networks and donor/acceptor domain sizes were obtained while maintaining the smooth surface morphology. By integrating with low-temperature-processed sol–gel ZnO electron extraction layer, power conversion efficiency (PCE) up to 4.4% under AM1.5G 1 sun illumination is achieved, compared to fast drying but low efficiency (1.2%) and high efficiency but with long-time solvent annealing treatment (4.3%) control cells deposited by spin coating in chlorobenzene (CB) and 1,2-dichlorobenzene (DCB) solution, respectively. The novel deposition technique reveals a promising process for highly efficient, high throughput, stable morphology organic solar cells fabrication. [Copyright &y& Elsevier]

With the rapid development of artificial intelligence, the simulation of the human brain for neuromorphic computing has demonstrated unprecedented progress. Photonic artificial synapses are strongly desirable owing to their higher neuron selectivity, lower crosstalk, wavelength multiplexing capabilities, and low operating power compared to their electric counterparts. This study demonstrates a highly transparent and flexible artificial synapse with a two‐terminal architecture that emulates photonic synaptic functionalities. This optically triggered artificial synapse exhibits clear synaptic characteristics such as paired‐pulse facilitation, short/long‐term memory, and synaptic behavior analogous to that of the iris in the human eye. Ultraviolet light illumination‐induced neuromorphic characteristics exhibited by the synapse are attributed to carrier trapping and detrapping in the SnO2 nanoparticles and CsPbCl3 perovskite interface. Moreover, the ability to detect deep red light without changes in synaptic behavior indicates the potential for dual‐mode operation. This study establishes a novel two‐terminal architecture for highly transparent and flexible photonic artificial synapse that can help facilitate higher integration density of transparent 3D stacking memristors, and make it possible to approach optical learning, memory, computing, and visual recognition. [ABSTRACT FROM AUTHOR]

We have used functionalized carbazoles and indenoquonoxalines as the main building units and enthynyl groups as the π-linkages to construct two novel dendritic fluorophores and studied their degenerate multi-photon absorption properties in both the solution phase and the neat-film state within femtosecond and nanosecond regions. In our experiments, these model compounds are found to manifest strong and widely dispersed two-photon absorption as well as effective power-limiting properties against ultra-short laser pulses in the near-IR region. In addition, both chromophores exhibit medium to strong three-photon-induced fluorescence, indicating such scaffold may serve as a reference structural motif for the development of three-photon materials. Image 1 • Two dendritic chromophores derived from carbazole and indenoquinoxaline units have been synthesized and characterized. • These fluorophores exhibit strong and wide dispersed two- and three-photon absorption in the near infrared (NIR) region. • Two-photon-based optical-power-limiting of a representative dye molecule is demonstrated in the femtosecond regime. • Two-photon-related properties of the spin-coated neat-film based on one of the model compound were studied. [ABSTRACT FROM AUTHOR]

Efficient solution-processed color-stable and color-tunable white organic light emitting diodes (OLEDs) have been realized by judicious selection of the host materials for the emission layers. The color-tunable OLED demonstrates the unique characteristic of modulating the electroluminescence by using the applied voltage of the device and displays color temperatures ranging from 1600 K to 4600 K around the daylight locus, with a peak external quantum efficiency of 13.6% and a peak current efficiency of 22.5 cd A −1 . On the other hand, the chromaticity-stable device shows a negligible color change, from 300 to 2000 nits. The manipulation of chromaticity is attributed to the energy transfer dynamics of the hosts and dopants under different electric fields. [ABSTRACT FROM AUTHOR]

Blade coating is applied to multi-layer phosphorescent OLED with five small-molecule hosts for the emission layer, including bis[3,5-di (9H-carbazol-9-yl)phenyl]diphenylsilane (SimCP2), 2,6-bis(3-(9H-carbazol-9-yl)phenyl) pyridine (26DCzPPy), 4,4′,4″-tris-( N -carbazolyl)-triphenylamine (TCTA), 9,9-bis[4-(3,6-di-tert-butylcarbazol-9-yl)phenyl]fluorene (TBCPF), and 2,7-bis(diphenylphosphoryl)-9,9′-spirobi[fluorene] (SPPO13). In general, blade coating gives low surface roughness around 0.2 nm without phase separation of the emitter and the host. In the large area of 2 cm by 3 cm the film thickness distribution is within 10% and uniform light-emission is achieved. 1,3-Bis[2-(4-tert-butylphenyl)-1,3,4-oxadiazo-5-yl]benzene (OXD-7) is added to tune the electron transport. Among all the hosts, 26DCzPPy and SimCP2 have by far the best electron–hole balance and consequently show the highest efficiency. For SimCP2, the maximal efficiency is 15.8 cd/A for blue and 24.2 cd/A for white emission. The order of efficiencies for the hosts is found to be quite different from the order in vacuum evaporation for the same device structures. [ABSTRACT FROM AUTHOR]

Highlights: [•] Different types of interconnection layers for tandem solar cells were investigated. [•] Spatial positions of sub-cells were designed to balance the photocurrent. [•] Highly efficient tandem cell with efficiency up to 7.4% were demonstrated. [ABSTRACT FROM AUTHOR]

Highlights: [•] The chromaticity of single EML solution-processed white OLEDs was investigated. [•] Correlation of CCT, CRI, and spectral designs was found. [•] The solution-processed quaternary doping white OLEDs were designed and fabricated. [•] White OLED with CRI=85, Du′v′ =+0.0009, EQE=13.7%, current efficiency=24.9cd/A at 1000cd/m2 was demonstrated. [ABSTRACT FROM AUTHOR]

Highlights: [•] Al–Au alloy as the cathode achieves an indium tin oxide (ITO)-free. [•] Al–Au alloy is spontaneously formed during the annealing of the active layer. [•] Al–Au alloy has low enough work function and high oxygen stability. [•] ITO-free solar cell shows PCE of 2.3% on metal substrate using blade coating. [Copyright &y& Elsevier]

Abstract: Blade coating with substrate heating and hot wind is demonstrated to be a general platform for multi-layer deposition of unmodified small-molecule organic semiconductors. Most unmodified small molecules, originally designed for vacuum evaporation, can be blade coated while the solubility is above 0.5wt.%. High uniformity is achieved for scale over 5cm. Orange devices by evaporation and blade coating are compared with 4,4′-bis(carbazol-9-yl)biphenyl (CBP) as the host, iridium(III) bis(4-(4-t-butylphenyl)thieno[3,2-c]pyridinato-N,C 2′)acetylacetonate (PO-01-TB) as the emitter. The efficiency difference is within 10%. When 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine (26DCzPPy) is used as the host, the current efficiencies are 40cd/A for orange, 32cd/A for green, and 20cd/A for blue. The optimized organic light-emitting diodes (OLED) structure developed for vacuum deposition can therefore be exactly copied by the low cost blade coating method in solution. [Copyright &y& Elsevier]

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

Abstract: We investigated the temporal coherence properties of organic light-emitting devices (OLEDs) by characterizing their coherence lengths. The interferometry based on the Newton’s rings apparatus was adopted to characterize the coherence lengths of various OLEDs, including non-doped/doped OLEDs and non-cavity bottom-emitting/cavity top-emitting OLEDs. The types of OLEDs investigated exhibit coherence lengths of 3–10μm, depending on the device structures/emitters and spectral bandwidths of the OLED emission. OLEDs using emitting molecules with more limited number of allowed vibronic transitions give narrower-band and more coherent emission. Introducing the microcavity into the device structure to induce resonance also narrows the emission spectra and meanwhile increases the coherence length. Such information may be useful for modeling, design, and optimization of optical properties of OLEDs. [Copyright &y& Elsevier]

Abstract: In typical organic light-emitting devices (OLEDs), a significant portion of internally generated radiation is trapped into the surface plasmon polariton (SPP) modes, in general not accessible for external use. By thinning the metal electrode, the SPP modes can be coupled to the outside surface of the device. As such, one can recycle a portion of SPPs by capping the thinned metal electrode with an appropriate absorbing/re-emission medium, inducing SPP-mediated energy transfer and re-emission. Such an approach may be used for implementing double-emitting OLEDs with different emission colors on two sides and with a broad color tuning capability. [Copyright &y& Elsevier]

[Display omitted] • First investigation for the panchromatic absorption from Sb based perovskites by using complimentary absorbing ETLs. • Adduct formation for ITIC molecule with Cs 3 Sb 2 I 9 have also been investigated. • Optical simulations were conducted to calculate the contribution to current density from each layer. • Best solar cell efficiency of 3.2% for inorganic Sb based perovskite was achieved. • A 3 B 2 X 9 perovskite is studied under indoor light illumination and an efficiency of 9.2% was achieved under 1000 Lux. The search for stable alternative lead-free perovskites has identified all-inorganic antimony/bismuth halide derivatives as promising materials. Despite attractive optoelectronic properties, their wider band gaps and poor morphological control have greatly limited their solar device performance. In this study, we used the indacenodithiophene-based organic acceptor (ITIC) as a Lewis base to improve the morphology of Cs 3 Sb 2 I 9 films and also as an electron transport layer to form a complimentary heterojunction, and, thereby, enhance the performance of Cs 3 Sb 2 I 9 solar cells. The presence of cyano and carbonyl groups in ITIC modulated the rate of crystallization of Cs 3 Sb 2 I 9 and improved its optoelectronic properties. The panchromatic absorption of the Cs 3 Sb 2 I 9 /ITIC heterostructure provided a power conversion efficiency of 3.25% in inverted solar cell structure under 1-sun irradiation. This enhanced performance when using a complimentary absorption strategy suggests a new pathway for developing wider-band-gap lead-free perovskite derivatives for solar cell applications. Moreover, the optimized Cs 3 Sb 2 I 9 /ITIC heterostructure–based solar cell achieved a PCE of 9.2% under indoor illumination at 1000 lx, highlighting the potential use of such devices in indoor applications. [ABSTRACT FROM AUTHOR]