Annulated Thienyl-Vinylene-Thienyl Building Blocks for π-Conjugated Copolymers: Ring Dimensions and Isomeric Structure Effects on π-Conjugation Length and Charge Transport

Abstract

A series of annulated thienyl-vinylene-thienyl (ATVT) building blocks having varied ring sizes, isomeric structures, and substituents was synthesized and characterized by spectroscopic, electrochemical, quantum chemical, and crystallographic methods. It is found that ATVT ring size and isomeric structure critically affect the planarity, structural rigidity, optical absorption, and redox properties of these new π-units. Various solubilizing substituents can be introduced on the annulated hydrocarbon fragments, preserving the ATVT planarity and redox properties. The corresponding πconjugated copolymers comprising ATVT units and electron-deficient units were also synthesized and characterized. The solubility, redox properties, and carrier transport behavior of these copolymers also depend remarkably on the annulated ring size and the ATVT unit isomeric structure. One of the copolymers composed of an ATVT with five-membered rings (1), (E)-4,4′,5,5′-tetrahydro-6,6′-bi(cyclopenta[b]thiophenylidene), and a naphthalenediimide (NDI) unit exhibits a broad UV−vis−NIR absorption with an onset beyond 1100 nm both in solution and in the film state, and thin films exhibit n-type semiconducting properties in field-effect transistors. These results are ascribed to the extended main chain π-conjugation length and the low HOMO−LUMO bandgap. Other π-conjugated copolymers containing unit 1 also exhibit characteristic red-shifted UV−vis−NIR absorption. A diketopyrrolopyrrole-based copolymer with unit 1 serves as an electron donor material in organic photovoltaic devices, exhibiting broad-range external quantum efficiencies from the UV to beyond 1000 nm.

Tuning the spectral, thermal and fluorescent properties of conjugated polymers via random copolymerization of hole transporting monomers

“…Therefore, hetero-structured devices are designed to facilitate charge injection and transport, via the insertion of additional charge transport layers in these polymers. 6,7 Such hetero-structured devices show degraded device performance due to phase separation by recrystallization. Controlling phase separation is perhaps the most attractive approach to simultaneously facilitate charge transfer and charge transport.…”

“…Controlling phase separation is perhaps the most attractive approach to simultaneously facilitate charge transfer and charge transport. [8][9][10] Chemists have found copolymerization technique to be one of the best feasible methods for the modication of various physiochemical and optoelectronic properties of homo-polymers as per end use application. 11,12 Conjugated copolymer systems offer the possibility to optimize and tailor electronic and optical properties such as energy transfer and charge transfer which is not feasible in homopolymers.…”

The opposite and amplifying effect of B ← N coordination on photophysical properties of regioisomers with an unsymmetrical backbone

“…Isomerism plays various important roles in chemistry, especially in medicinal and pharmaceutical chemistry 1. In the areas of optoelectronics and materials science,2 isomers with varying substitution patterns also attract great research interest due to their distinct properties, which allows them to be used for fine-tuning molecular functions in both bulk materials and devices. Therefore, understanding and exploiting the influence of isomerism on the physical and photophysical properties of molecules is an important issue in materials science.…”

The Effect of Donor and Nonfullerene Acceptor Inhomogeneous Distribution within the Photoactive Layer on the Performance of Polymer Solar Cells with Different Device Structures

“…Recently, non-fullerene small molecules and all-polymer (using a p -type donor polymer and an n -type acceptor polymer) solar cells have emerged. Compared with fullerene derivatives, non-fullerene n -type small molecule and polymer acceptors can be flexibly designed to match the donor polymer in molecular weight, absorption spectra and energy level, allowing a better device performance [ 8 , 9 , 10 , 11 ]. Up to date, the PCE of non-fullerene acceptor based devices has exceeded 13% [ 5 ].…”