Rational Design of a Multifunctional Benzothiadiazole Derivative in Organic Photonics and Electronics.

In order to achieve a multifunctional compound with potential application in organic photonics and electronics, a multidonor benzothiadiazole derivative was rationally designed and synthesized employing microwave irradiation as energy source, increasing the process efficiency about yields and reaction times in comparison with conventional conditions. This powerful compound displayed solvatochromism and showed efficient behavior as red optical waveguide with low OLC around 10-2  dB µm-1 and with the capacity of light transmission in two directions. In addition, the proposed derivative acted as efficient p-type semiconductor in organic field-effect transistors (OFETs) with hole mobilities up 10-1  cm2  V-1 s-1 . This corroborates its multifunctional character, thus making it a potential candidate to be applied in hybrid organic field-effect optical waveguides (OFEWs).

Donor-Acceptor-Donor 1H-Benzo[d]imidazole Derivatives as Optical Waveguides.

A new series of donor-acceptor-donor (D-A-D) structures derived from arylethynyl 1H-benzo[d]imidazole was synthesized and processed into single crystals with the goal of testing such crystals' ability to act as optical waveguides. Some crystals displayed luminescence in the 550-600 nm range and optical waveguiding behavior with optical loss coefficients around 10-2 dB/µm, which indicated a notable light transport. The crystalline structure, confirmed by X-ray diffraction, contains internal channels that are important for light propagation, as we previously reported. The combination of a 1D assembly, a single crystal structure, and notable light emission properties with low losses from self-absorption made 1H-benzo[d]imidazole derivatives appealing compounds for optical waveguide applications.

Mechanical Processing of Naturally Bent Organic Crystalline Microoptical Waveguides and Junctions.

Precise mechanical processing of optical microcrystals involves complex microscale operations viz. moving, bending, lifting, and cutting of crystals. Some of these mechanical operations can be implemented by applying mechanical force at specific points of the crystal to fabricate advanced crystalline optical junctions. Mechanically compliant flexible optical crystals are ideal candidates for the designing of such microoptical junctions. A vapor-phase growth of naturally bent optical waveguiding crystals of 1,4-bis(2-cyanophenylethynyl)benzene (1) on a surface forming different optical junctions is presented. In the solid-state, molecule 1 interacts with its neighbors via CH⋅⋅⋅N hydrogen bonding and π-π stacking. The microcrystals deposited at a glass surface exhibit moderate flexibility due to substantial surface adherence energy. The obtained network crystals also display mechanical compliance when cut precisely with sharp atomic force microscope cantilever tip, making them ideal candidates for building innovative T- and Δ-shaped optical junctions with multiple outputs. The presented micromechanical processing technique can also be effectively used as a tool to fabricate single-crystal integrated photonic devices and circuits on suitable substrates.

Extended Alkenyl and Alkynyl Benzotriazoles with Enhanced Two-Photon Absorption Properties as a Promising Alternative to Benzothiadiazoles.

A series of donor-π-acceptor-π-donor (D-π-A-π-D) benzoazole dyes with 2H-benzo[d][1,2,3]triazole or BTD cores have been prepared and their photophysical properties characterized. The properties of these compounds display remarkable differences, mainly as a result of the electron-donor substituent. Dyes with the best properties have visible-light absorption over λ=400 nm, large Stokes shifts in the range of about 3500-6400 cm-1 , and good fluorescence emission with quantum yields of up to 0.78. The two-photon absorption properties were also studied to establish the relationship between structure and properties in the different compounds synthesized. These results provided cross sections of up to 1500 GM, with a predominance of S2 ←S0 transitions and a high charge-transfer character. Time-dependent DFT calculations supported the experimental results.

Tunable Unexplored Luminescence in Waveguides Based on D-A-D Benzoselenadiazoles Nanofibers.

A set of novel Donor-Acceptor-Donor (D-A-D) benzoselenadiazole derivatives has been synthesized and crystallized in nanocrystals in order to explore the correlation between their chemical structure and the waveguided luminescent properties. The findings reveal that all crystals exhibit luminescence and active optical waveguiding, demonstrating the ability to adjust their luminescence within a broad spectral range of 550-700 nm depending on the donor group attached to the benzoselenadiazole core. Notably, a clear relationship exists between the HOMO-LUMO energy gaps of each compound and the color emission of the corresponding optical waveguides. These outcomes affirm the feasibility of modifying the color emission of organic waveguides through suitable chemical functionalization. Importantly, this study marks the first utilization of benzoseleniadiazole derivatives for such purposes, underscoring the originality of this research. In addition, the obtention of nanocrystals is a key tool for the implementation of miniaturized photonic devices.

Recent Insights about the Role of Gels in Organic Photonics and Electronics.

This review article provides an in-depth exploration of the role of gels in the fields of organic electronics and photonics, focusing on their unique properties and applications. Despite their remarkable potential, gel-based innovations remain relatively uncharted in these domains. This brief review aims to bridge the knowledge gap by shedding light on the diverse roles that gels can fulfil in the enhancement of organic electronic and photonic devices. From flexible electronics to light-emitting materials, we delve into specific examples of gel applications, highlighting their versatility and promising outcomes. This work serves as an indispensable resource for researchers interested in harnessing the transformative power of gels within these cutting-edge fields. The objective of this review is to raise awareness about the overlooked research potential of gels in optoelectronic materials, which have somewhat diminished in recent years.

Polarised Optical Emission from Organic Anisotropic Microoptical Waveguides Grown by Ambient Pressure Vapour-deposition.

Ambient pressure chemical vapour deposition of 5,5'-bis((2-(trifluoromethyl)phenyl)ethynyl)-2,2'-bithiophene provides ultrapure needle-shaped crystals. The crystal's supramolecular structure consists of an array of hydrogen bonds and π-π interactions leading to anisotropic arrangements. The cyan emitting crystals exhibit an optical waveguiding tendency with guided polarised optical emissions due to anisotropic molecular arrangements.

D-A-D 2H-benzo[d][1,2,3]triazole derivatives as p-type semiconductors in organic field-effect transistors.

A series of Donor-π-Acceptor-π-Donor compounds based on a 2H-benzo[d][1,2,3]triazole core branched with different alkynyl donor groups has been characterized and tested in organic field-effect transistors (OFETs). The electronic and molecular structures were elucidated through optical and vibrational spectroscopy in conjunction with DFT calculations. The results indicate that the planarity of the structure and the good intramolecular charge transfer from the electron-donating to the electron-withdrawing fragments play a critical role in the application of the compounds as semiconductors in OFET devices. The compounds were tested in a top-contact/bottom-gate thin film transistor architecture, and they behave as p-type semiconductors.