Dithienylbenzobis(thiadiazole) based organic semiconductors with low LUMO levels and narrow energy gaps

The band gap, EG, of an organic solid can be estimated by adding the magnitudes of oxidation and reduction potentials of the compound in solution, plus a correction to the ion solvation energy which allows for the different dielectric constants of solvent and solid. Values of EG for 30 organic solids have been estimated. �� The auto-ionization model, previously used for aromatic hydrocarbons, is applied to dyes and chlorophylls. The values of EG are used to interpret various existing results on photoconduction and semiconduction in dyes and chlorophylls.

Download Full-text

Quinoid‐aromatic Resonance for Very Small Optical Energy Gaps in Small‐molecule Organic Semiconductors: a Naphthodithiophenedione‐oligothiophene triad system

Chemistry - A European Journal ◽

10.1002/chem.202102663 ◽

2021 ◽

Author(s):

Kazuo Takimiya ◽

Kohsuke Kawabata

Keyword(s):

Organic Semiconductors ◽

Small Molecule ◽

Optical Energy ◽

Energy Gaps ◽

Optical Energy Gaps

Download Full-text

ChemInform Abstract: Dithienylbenzobis(thiadiazole) Based Organic Semiconductors with Low LUMO Levels and Narrow Energy Gaps.

ChemInform ◽

10.1002/chin.201035137 ◽

2010 ◽

Vol 41 (35) ◽

pp. no-no

Author(s):

Takahiro Kono ◽

Daisuke Kumaki ◽

Jun-ichi Nishida ◽

Shizuo Tokito ◽

Yoshiro Yamashita

Keyword(s):

Organic Semiconductors ◽

Energy Gaps

Download Full-text

Energetic Control of Redox-Active Polymers Towards Safe Organic Bioelectronic Materials

10.26434/chemrxiv.11366186.v1 ◽

2019 ◽

Author(s):

Alexander Giovannitti ◽

Reem B. Rashid ◽

Quentin Thiburce ◽

Bryan D. Paulsen ◽

Camila Cendra ◽

...

Keyword(s):

Molecular Oxygen ◽

Organic Semiconductors ◽

Side Reaction ◽

Semiconducting Polymers ◽

Side Reactions ◽

Redox Active ◽

Donor Acceptor ◽

Electrochemical Devices ◽

Biological Environment ◽

Device Operation

Avoiding faradaic side reactions during the operation of electrochemical devices is important to enhance the device stability, to achieve low power consumption, and to prevent the formation of reactive side‑products. This is particularly important for bioelectronic devices which are designed to operate in biological systems. While redox‑active materials based on conducting and semiconducting polymers represent an exciting class of materials for bioelectronic devices, they are susceptible to electrochemical side‑reactions with molecular oxygen during device operation. We show that this electrochemical side reaction yields hydrogen peroxide (H2O2), a reactive side‑product, which may be harmful to the local biological environment and may also accelerate device degradation. We report a design strategy for the development of redox-active organic semiconductors based on donor-acceptor copolymers that prevent the formation of H2O2 during device operation. This study elucidates the previously overlooked side-reactions between redox-active conjugated polymers and molecular oxygen in electrochemical devices for bioelectronics, which is critical for the operation of electrolyte‑gated devices in application-relevant environments.

Download Full-text

Quantitative Image Analysis of Fractal-like Thin Films of Organic Semiconductors

10.26434/chemrxiv.6223610.v1 ◽

2018 ◽

Author(s):

Weikun Zhu ◽

Erfan Mohammadi ◽

Ying Diao

Keyword(s):

Thin Film ◽

Thin Films ◽

Image Analysis ◽

Fractal Dimension ◽

Organic Semiconductors ◽

Film Growth ◽

Electronic Device ◽

Significant Control ◽

Semiconductor Thin Films ◽

Two Parameters

Morphology modulation offers significant control over organic electronic device performance. However, morphology quantification has been rarely carried out via image analysis. In this work, we designed a MATLAB program to evaluate two key parameters describing morphology of small molecule semiconductor thin films: fractal dimension and film coverage. We then employ this program in a case study of meniscus-guided coating of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) under various conditions to analyze a diverse and complex morphology set. The evolution of morphology in terms of fractal dimension and film coverage was studied as a function of coating speed. We discovered that combined fractal dimension and film coverage can quantitatively capture the key characteristics of C8-BTBT thin film morphology; change of these two parameters further inform morphology transition. Furthermore, fractal dimension could potentially shed light on thin film growth mechanisms.

Download Full-text

Design and Synthesis of Two-Dimensional Covalent Organic Frameworks with Four-Arm Cores: Prediction of Remarkable Ambipolar Charge-Transport Properties

10.26434/chemrxiv.7766786.v2 ◽

2019 ◽

Author(s):

Simil Thomas ◽

Hong Li ◽

Raghunath R. Dasari ◽

Austin Evans ◽

William Dichtel ◽

...

Keyword(s):

Charge Transport ◽

Organic Semiconductors ◽

Density Functional ◽

Polymer Networks ◽

Two Dimensional ◽

Covalent Organic Frameworks ◽

X Ray Diffraction ◽

Zinc Porphyrin ◽

Design And Synthesis ◽

Predicted Values

We have considered three two-dimensional (2D) π-conjugated polymer networks (i.e., covalent organic frameworks, COFs) materials based on pyrene, porphyrin, and zinc-porphyrin cores connected via diacetylenic linkers. Their electronic structures, investigated at the density functional theory global-hybrid level, are indicative of valence and conduction bands that have large widths, ranging between 1 and 2 eV. Using a molecular approach to derive the electronic couplings between adjacent core units and the electron-vibration couplings, the three π-conjugated 2D COFs are predicted to have ambipolar charge-transport characteristics with electron and hole mobilities in the range of 65-95 cm2V-1s-1. Such predicted values rank these 2D COFs among the highest-mobility organic semiconductors. In addition, we have synthesized the zinc-porphyrin based 2D COF and carried out structural characterization via powder X-ray diffraction and surface area analysis, which demonstrates the feasability of these electroactive networks.

Download Full-text

Clustering-Triggered Efficient Room Temperature Phosphorescence from Nonconventional Luminophores

10.26434/chemrxiv.9959132 ◽

2019 ◽

Author(s):

Shuyuan Zheng ◽

Taiping Hu ◽

Xin Bin ◽

Yunzhong Wang ◽

Yuanping Yi ◽

...

Keyword(s):

Room Temperature ◽

High Efficiency ◽

Spin Orbit Coupling ◽

Design Rationale ◽

Emission Mechanism ◽

Room Temperature Phosphorescence ◽

Electronic Interactions ◽

Energy Gaps ◽

Theoretical Results

Pure organic room temperature phosphorescence (RTP) and luminescence from nonconventional luminophores have gained increasing attention. However, it remains challenging to achieve efficient RTP from unorthodox luminophores, on account of the unsophisticated understanding of the emission mechanism. Here we propose a strategy to realize efficient RTP in nonconventional luminophores through incorporation of lone pairs together with clustering and effective electronic interactions. The former promotes spin-orbit coupling and boost the consequent intersystem crossing, whereas the latter narrows energy gaps and stabilizes the triplets, thus synergistically affording remarkable RTP. Experimental and theoretical results of urea and its derivatives verify the design rationale. Remarkably, RTP from thiourea solids with unprecedentedly high efficiency of up to 24.5% is obtained. Further control experiments testify the crucial role of through-space delocalization on the emission. These results would spur the future fabrication of nonconventional phosphors, and moreover should advance understanding of the underlying emission mechanism.

Download Full-text