Ultra-Narrowband Near-Infrared Responsive J-Aggregates of Fused Quinoidal Tetracyanoindacenodithiophene

Oxindole-Terminated Quinoidal Compounds with Ultrahigh Electron Affinity: Synthesis and Applications

Six quinoidal compounds terminated by oxindole have been synthesized via selective nucleophilic addition, dehydroxylation, and oxidation. Through the modification of the quinoidal core and terminal benzene rings with fluoride atoms or cyano groups, the LUMO energy levels of the quinoidal compounds can be tuned within the range -4.05 to -4.54 eV. The quinoidal molecules exhibited electron transport behavior and can be used as dopants to dope an oligo(ethylene glycol)-substituted polythiophene.

Supramolecular Engineering of Narrow Absorption Bands by Exciton Coupling in Pristine and Mixed Solid-State Dye Aggregates

Tunability of functional properties in a continuous manner is desired but challenging to accomplish for organic solid-state materials. Herein, we describe a method for tuning optoelectronic properties of solid-state aggregates with narrow absorption bands. First, we systematically shift the absorption maxima of highly dipolar merocyanine dyes in solution by chemical alterations of their chromophore cores. This leaves their solid-state packing arrangements unchanged, affording similar J- and H-coupled aggregate absorption bands at different wavelengths. Next, mixing these isostructural dyes leads to a spectral fine-tuning of the mixed layers, which could be characterized as crystalline organic solid solutions and utilized in narrowband color-selective organic photodiodes. Finally, we devise a semiempirical model, which explains the observed spectral tuning in terms of the molecular exciton theory. Thus, we demonstrate narrowband absorbing solid-state aggregates spanning the wavelength range of 437-760 nm, whose absorption can be fine-tuned over 40% of the visible light range.

Multi-Resonance 1,4-BN-Heteroarene for Filterless Narrowband Photodetector

As an emerging class of optoelectronic materials, multi-resonance (MR) 1,4-BN-heteroarenes have been extensively employed as narrowband electroluminescence materials, whereas their absorption feature has largely been neglected. Here we construct the first MR-molecule-based phototransistor for filterless narrowband photodetectors (NBPDs) by anchoring narrowband absorption MR molecules on a high-mobility semiconductor indium-zinc-oxide (IZO) film. The resulting device exhibits high-performance photodetection with a small full-width at half-maximum (FWHM) of 33 nm, which represents a new record for NBPDs based on intrinsic narrowband absorbing materials. These results demonstrate the great potential of MR materials as a new molecular platform for developing high-performance NBPDs.

High External Quantum Efficiency and Ultra-Narrowband Organic Photodiodes Using Single-Component Photoabsorber With Multiple-Resonance Effect

Organic photodiodes (OPDs) that utilize wavelength-selective absorbing molecules offer a direct approach to capturing specific wavelengths of light in multispectral sensors/imaging systems without filters. However, they exhibit broad response bandwidths, low external quantum efficiency (EQE), and often require compromises in two-component photoactive materials. Herein, the first utility of boron-nitrogen (BN) single-component photoabsorbers, leveraging a multi-resonance effect are introduced to attain OPDs with both record-high EQE of 33.77% and ultra-small full-width half-maximum (FWHM) of 36 nm in the reported narrowband OPDs using single-component photoabsorbers. It is found that the outstanding performance of these narrowband OPDs can be attributed to the ultra-small FWHM, slow charge recombination, low activation energy, and balanced bipolar charge transport within the para-tert-butyl substituted B,N-embedded rigid polycyclic molecule (BNCz) film. Furthermore, BN derivatives such as BN(p)SCH3, BN(p)SO2CH3, and pyBN-m-H have also shown high EQE, minimal FWHM, and tunable photoresponse peaks ranging from blue-violet to blue-turquoise, highlighting the potential of BN molecules and molecular engineering in the development of novel narrowband absorbers for advanced wavelength-selective OPDs. Such pioneering working can provide a class of novel narrowband absorbers to propel the advancement of high-performance wavelength-selective OPDs.

Ultrathin near-infrared transmitting films enabled by deprotonation-induced intramolecular charge transfer of a dopant

Near-infrared transparent films demonstrate important applications in many fields, but how to eliminate light interference from ultraviolet-visible region and how to tackle the trade-off effect between film thickness and transmittance remain as challenges. Herein, we report a near-infrared transparent film that achieves high-efficient combination of thin thickness (16 μm), suitable cut-off wavelength (890 nm), and ideal transmittance (TNIR > 90%, TVis < 1%). Moreover, the film is photo-chemically stable, heating resistance and moisture insensitive. The key component of the film is a complex of a specially designed boron compound containing a perylene monoimide unit (PMI-CBN) with an organic base 1,8-diazabicyclo[5,4,0]undec-7-ene. The complex depicts red-shifted absorption from 709 to 943 nm owing to deprotonation of the N-H group of PMI-CBN. Dispersion of the complex in polymethyl methacrylate results in the high-performance film. As demos, the film is successfully used for night vision imaging and information encryption.

The Aggregation Units of J-Aggregates: Transitioning from Monomers to Hydrogen-Bonded Dimers

In recent years, J-aggregates, as supramolecular assembly structures, have increasingly attracted scientific interest. Currently, the prevailing consensus is that J-aggregates are formed through the interleaved stacking of monomers arranged in parallel. However, our findings suggest that the fundamental units constituting J-aggregates are not limited to monomers alone but also encompass molecular aggregates interconnected by noncovalent bonds, which we designate as aggregation units. We have synthesized three asymmetric pyrrolopyrrole cyanine (PPCy) dyes capable of forming hydrogen-bonded dimers and have verified that these hydrogen-bonded dimers can serve as aggregation units to generate J-aggregates. The detailed structural and optical properties revealed that the J-aggregates of these dyes exhibited a significantly red-shifted and narrowed emission in the near-infrared (NIR) fluorescence compared to the monomers.

A Conjugated Carboranyl Main Chain Polymer with Aggregation-Induced Emission in the Near-Infrared

Materials exhibiting aggregation-induced emission (AIE) are both highly emissive in the solid state and prompt a strongly red-shifted emission and should therefore pose as good candidates toward emerging near-infrared (NIR) applications of organic semiconductors (OSCs). Despite this, very few AIE materials have been reported with significant emissivity past 700 nm. In this work, we elucidate the potential of ortho-carborane as an AIE-active component in the design of NIR-emitting OSCs. By incorporating ortho-carborane in the backbone of a conjugated polymer, a remarkable solid-state photoluminescence quantum yield of 13.4% is achieved, with a photoluminescence maximum of 734 nm. In contrast, the corresponding para and meta isomers exhibited aggregation-caused quenching. The materials are demonstrated for electronic applications through the fabrication of nondoped polymer light-emitting diodes. Devices employing the ortho isomer achieved nearly pure NIR emission, with 86% of emission at wavelengths longer than 700 nm and an electroluminescence maximum at 761 nm, producing a significant light output of 1.37 W sr-1 m-2.

Retinomorphic Motion Detector Fabricated with Organic Infrared Semiconductors

Organic retinomorphic sensors offer the advantage of in-sensor processing to filter out redundant static backgrounds and are well suited for motion detection. To improve this promising structure, here, the key role of interfacial energetics in promoting charge accumulation to raise the inherent photoresponse of the light-sensitive capacitor is studied. Specifically, incorporating appropriate interfacial layers around the photoactive layer is crucial to extend the carrier lifetime, as confirmed by intensity-modulated photovoltage spectroscopy. Compared to its photodiode counterpart, the retinomorphic sensor shows better detectivity and response speed due to the additional insulating layer, which reduces the dark current and the RC time constant. Lastly, three retinomorphic sensors are integrated into a line array to demonstrate the detection of movement speed and direction, showing the potential of retinomorphic designs for efficient motion tracking.

Enantiopure J-Aggregate of Quaterrylene Bisimides for Strong Chiroptical NIR-Response

Chiral polycyclic aromatic hydrocarbons can be tailored for next-generation photonic materials by carefully designing their molecular as well as supramolecular architectures. Hence, excitonic coupling can boost the chiroptical response in extended aggregates but is still challenging to achieve by pure self-assembly. Whereas most reports on these potential materials cover the UV and visible spectral range, systems in the near infrared (NIR) are underdeveloped. We report a new quaterrylene bisimide derivative with a conformationally stable twisted π-backbone enabled by the sterical congestion of a fourfold bay-arylation. Rendering the π-subplanes accessible by small imide substituents allows for a slip-stacked chiral arrangement by kinetic self-assembly in low polarity solvents. The well dispersed solid-state aggregate reveals a sharp optical signature of strong J-type excitonic coupling in both absorption (897 nm) and emission (912 nm) far in the NIR region and reaches absorption dissymmetry factors up to 1.1 × 10^-2. The structural elucidation was achieved by atomic force microscopy and single-crystal X-ray analysis which we combined to derive a structural model of a fourfold stranded enantiopure superhelix. We could deduce that the role of phenyl substituents is not only granting stable axial chirality but also guiding the chromophore into a chiral supramolecular arrangement needed for strong excitonic chirality.