Photochemical reaction enabling the engineering of photonic spin-orbit coupling in organic-crystal optical microcavities

The control and active manipulation of spin-orbit coupling (SOC) in photonic systems is fundamental in the development of modern spin optics and topological photonic devices. Here, we demonstrate the control of an artificial Rashba-Dresselhaus (RD) SOC mediated by photochemical reactions in a microcavity filled with an organic single-crystal of photochromic phase-change character. Splitting of the circular polarization components of the optical modes induced by photonic RD SOC is observed experimentally in momentum space. By applying an ultraviolet light beam, we control the spatial molecular orientation through a photochemical reaction and with that we control the energies of the photonic modes. This way we realize a reversible conversion of spin-splitting of the optical modes with different energies, leading to an optically controlled switching between circularly and linearly polarized emission from our device. Our strategy of in situ and reversible engineering of SOC induced by a light field provides a promising approach to actively design and manipulate synthetic gauge fields towards future on-chip integration in photonics and topological photonic devices

Dithieno[2,3-d;2 ',3 '-d ']benzo[1,2-b;4,5-b ']-dithiophene based organic sensitizers for dye-sensitized solar cells

We report two novel D-pi-A type organic dyes with a coplanar dithieno[2,3-d; 2',3'-d']benzo[1,2 b;4,5-b']dithiophene (DTBDT) as pi-spacer for dye-sensitized solar cells. A best device performance with a power conversion efficiency of 6.32% is achieved, making DTBDT unit a promising building block for design of organic sensitizers

Cyclopentadithiophene-Benzothiadiazole Donor-Acceptor polymers as prototypical semiconductors for high-performance field-effect transistors

Donor-acceptor (D-A) conjugated polymers are of great interest as organic semiconductors, because they offer a rational tailoring of the electronic properties by modification of the donor and acceptor units. Nowadays, D-A polymers exhibit field-effect mobilities on the order of 10 -2-10 0 cm 2 V -1 s -1, while several examples showed a mobility over 10 cm 2 V -1 s -1. The development of cyclopentadithiophene-benzothiadiazole (CDT-BTZ) copolymers one decade ago represents an important step toward high-performance organic semiconductors for field-effect transistors. The significant rise in field-effect mobility of CDT-BTZ in comparison to the existing D-A polymers at that time opened the door to a new research field with a large number of novel D-A systems. From this point, the device performance of CDT-BTZ was gradually improved by a systematic optimization of the synthesis and polymer structure as well as by an efficient solution processing into long-range ordered thin films. The key aspect was a comprehensive understanding of the relation between polymer structure and solid-state organization. Due to their fundamental role for the field of D-A polymers in general, this Account will for the first time explicitly focus on prototypical CDT-BTZ polymers, while other reviews provide an excellent general overview on D-A polymers. The first part of this Account discusses strategies for improving the charge carrier transport, focusing on chemical aspects. Improved synthesis as an essential stage toward high purity, and high molecular weight is a prerequisite for molecular order. The modification of substituents is a further crucial feature to tune the CDT-BTZ packing and self-assembly. Linear alkyl side chains facilitate intermolecular π-stacking interactions, while branched ones increase solubility and alter the polymer packing. Additional control over the supramolecular organization of CDT-BTZ polymers is introduced by alkenyl substituents via their cis-trans isomerization. The last discussed chemical concept is based on heteroatom variation within the CDT unit. The relationships found experimentally for CDT-BTZ between polymer chemical structure, solid-state organization, and charge carrier transport are explained by means of theoretical simulations. Besides the effects of molecular design, the second part of this Account discusses the processing conditions from solution. The film microstructure, defined as a mesoscopic domain organization, is critically affected by solution processing. Suitable processing techniques allow the formation of a long-range order and a uniaxial orientation of the CDT-BTZ chains, thus lowering the trapping density of grain boundaries for charge carriers. For instance, alignment of the CDT-BTZ polymer by dip-coating yields films with a pronounced structural and electrical anisotropy and favors a fast migration of charge carriers along the conjugated backbones in the deposition direction. By using film compression with the assistance of an ionic liquid, one even obtains CDT-BTZ films with a band-like transport and a transistor hole mobility of 10 cm 2 V -1 s -1. This device performance is attributed to large domains in the compressed films being formed by CDT-BTZ with longer alkyl chains, which establish a fine balance between polymer interactions and growth kinetics during solvent evaporation. On the basis of the prototypical semiconductor CDT-BTZ, this Account provides general guidelines for achieving high-performance polymer transistors by taking into account the subtle balance of synthetic protocol, molecular design, and processing

Cyclopentadithiophene-Benzothiadiazole Donor-Acceptor polymers as prototypical semiconductors for high-performance field-effect transistors

\u3cp\u3eDonor-acceptor (D-A) conjugated polymers are of great interest as organic semiconductors, because they offer a rational tailoring of the electronic properties by modification of the donor and acceptor units. Nowadays, D-A polymers exhibit field-effect mobilities on the order of 10 -2-10 0 cm 2 V -1 s -1, while several examples showed a mobility over 10 cm 2 V -1 s -1. The development of cyclopentadithiophene-benzothiadiazole (CDT-BTZ) copolymers one decade ago represents an important step toward high-performance organic semiconductors for field-effect transistors. The significant rise in field-effect mobility of CDT-BTZ in comparison to the existing D-A polymers at that time opened the door to a new research field with a large number of novel D-A systems. From this point, the device performance of CDT-BTZ was gradually improved by a systematic optimization of the synthesis and polymer structure as well as by an efficient solution processing into long-range ordered thin films. The key aspect was a comprehensive understanding of the relation between polymer structure and solid-state organization. Due to their fundamental role for the field of D-A polymers in general, this Account will for the first time explicitly focus on prototypical CDT-BTZ polymers, while other reviews provide an excellent general overview on D-A polymers. The first part of this Account discusses strategies for improving the charge carrier transport, focusing on chemical aspects. Improved synthesis as an essential stage toward high purity, and high molecular weight is a prerequisite for molecular order. The modification of substituents is a further crucial feature to tune the CDT-BTZ packing and self-assembly. Linear alkyl side chains facilitate intermolecular π-stacking interactions, while branched ones increase solubility and alter the polymer packing. Additional control over the supramolecular organization of CDT-BTZ polymers is introduced by alkenyl substituents via their cis-trans isomerization. The last discussed chemical concept is based on heteroatom variation within the CDT unit. The relationships found experimentally for CDT-BTZ between polymer chemical structure, solid-state organization, and charge carrier transport are explained by means of theoretical simulations. Besides the effects of molecular design, the second part of this Account discusses the processing conditions from solution. The film microstructure, defined as a mesoscopic domain organization, is critically affected by solution processing. Suitable processing techniques allow the formation of a long-range order and a uniaxial orientation of the CDT-BTZ chains, thus lowering the trapping density of grain boundaries for charge carriers. For instance, alignment of the CDT-BTZ polymer by dip-coating yields films with a pronounced structural and electrical anisotropy and favors a fast migration of charge carriers along the conjugated backbones in the deposition direction. By using film compression with the assistance of an ionic liquid, one even obtains CDT-BTZ films with a band-like transport and a transistor hole mobility of 10 cm 2 V -1 s -1. This device performance is attributed to large domains in the compressed films being formed by CDT-BTZ with longer alkyl chains, which establish a fine balance between polymer interactions and growth kinetics during solvent evaporation. On the basis of the prototypical semiconductor CDT-BTZ, this Account provides general guidelines for achieving high-performance polymer transistors by taking into account the subtle balance of synthetic protocol, molecular design, and processing. \u3c/p\u3

Synthesis of a quinoidal dithieno[2,3-D;2′,3′- d] benzo[2,1- b;3,4- b ′]-dithiophene based open-shell singlet biradicaloid

A fused heteroacene derivative, bis(dicyanomethylene)-end-capped-dithieno[2,3-d;2′,3′-d]benzo[2,1-b;3,4-b′]-dithiophene (4CN-DTmBDT) was synthesized.</p

Condensed Derivatives of Thiadiazoloquinoxaline as Strong Acceptors

Three novel thiadiazoloquinoxaline (TQ) derivatives, <b>TIPS-APhTQ</b>, <b>TIPS-PhTQ</b>, and <b>TIPS-BDTTQ</b>, were synthesized by introducing two triisopropylsilylethynyl groups and alternating the aromatic ring units in the condensed moiety of TQ. The synthetic route is very efficient, providing high yields. Cyclic voltammetry suggests high electron affinity values of −3.82, −3.95, and −3.99 eV for <b>TIPS-APhTQ</b>, <b>TIPS-PhTQ</b>, and <b>TIPS-BDTTQ</b>, respectively. Single-crystal X-ray diffraction reveals that three molecules form corresponding dimers by intermolecular S–N interaction and have very similar two-dimensional π-stacking. The π-stacking distances between them are as close as 3.34–3.46 Å

Condensed Derivatives of Thiadiazoloquinoxaline as Strong Acceptors

Three novel thiadiazoloquinoxaline (TQ) derivatives, <b>TIPS-APhTQ</b>, <b>TIPS-PhTQ</b>, and <b>TIPS-BDTTQ</b>, were synthesized by introducing two triisopropylsilylethynyl groups and alternating the aromatic ring units in the condensed moiety of TQ. The synthetic route is very efficient, providing high yields. Cyclic voltammetry suggests high electron affinity values of −3.82, −3.95, and −3.99 eV for <b>TIPS-APhTQ</b>, <b>TIPS-PhTQ</b>, and <b>TIPS-BDTTQ</b>, respectively. Single-crystal X-ray diffraction reveals that three molecules form corresponding dimers by intermolecular S–N interaction and have very similar two-dimensional π-stacking. The π-stacking distances between them are as close as 3.34–3.46 Å

Highly Ordered Phenanthroline-Fused Azaacene

A new synthetic route to prepare a centrosymmetric phenanthroline-fused azaacene derivative, <b>TIPS-BisPhNPQ</b>, is described. Another axialsymmetric analogue, <b>TIPS-PhNTQ</b>, is also synthesized for comparison. Cyclic voltammetry measurements indicate high electron affinity values of −4.03 and −4.01 eV for <b>TIPS-PhNTQ</b> and <b>TIPS-BisPhNPQ</b>, respectively. Single-crystal X-ray diffraction reveals that <b>TIPS-PhNTQ</b> forms dimers by intermolecular S–N and N–N interaction, while <b>TIPS-BisPhNPQ</b> shows a highly ordered arrangement via two-dimensional brickwork packing and intermolecular hydrogen bonding. The synthetic protocol established in this paper should be highly applicable to the preparation of more azaacene derivatives with extended π-conjugations

CCDC 1414138: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures