Hole Injection Role of p-Type Conjugated Polymer Nanolayers in Phosphorescent Organic Light-Emitting Devices

Effects of Different Lengths of Oligo (Ethylene Glycol) Side Chains on the Electrochromic and Photovoltaic Properties of Benzothiadiazole-Based Donor-Acceptor Conjugated Polymers

In recent years, donor-acceptor (D-A)-type conjugated polymers have been widely used in the field of organic solar cells (OSCs) and electrochromism (EC). Considering the poor solubility of D-A conjugated polymers, the solvents used in material processing and related device preparation are mostly toxic halogenated solvents, which have become the biggest obstacle to the future commercial process of the OSC and EC field. Herein, we designed and synthesized three novel D-A conjugated polymers, PBDT1-DTBF, PBDT2-DTBF, and PBDT3-DTBF, by introducing polar oligo (ethylene glycol) (OEG) side chains of different lengths in the donor unit benzodithiophene (BDT) as side chain modification. Studies on solubility, optics, electrochemical, photovoltaic and electrochromic properties are conducted, and the influence of the introduction of OEG side chains on its basic properties is also discussed. Studies on solubility and electrochromic properties show unusual trends that need further research. However, since PBDT-DTBF-class polymers and acceptor IT-4F failed to form proper morphology under the low-boiling point solvent THF solvent processing, the photovoltaic performance of prepared devices is not ideal. However, films with THF as processing solvent showed relatively desirable electrochromic properties and films cast from THF display higher CE than CB as the solvent. Therefore, this class of polymers has application feasibility for green solvent processing in the OSC and EC fields. The research provides an idea for the design of green solvent-processable polymer solar cell materials in the future and a meaningful exploration of the application of green solvents in the field of electrochromism.

Derivatives of diphenylamine and benzothiadiazole in optoelectronic applications: a review

Light-emitting conjugated organic compounds have found special interest among researchers. Because of their adjustable optoelectronic properties they can be applied in e.g. field-effect transistors, sensors, light-emitting diodes or photovoltaic cells. In order to develop high-performance systems, it is important to understand the relationship between the structure and the photophysical properties of the material used. One of the employed strategies is to decrease the band gap of conjugated compounds, often achieved through a “donor–acceptor” approach. One of the popular groups applied as an electron-accepting unit are benzothiadiazoles, while diphenylamine exhibits good electron-donating ability. The functional groups can affect the energy levels of materials, influencing the color of the light emitted. This work presents a review of research focused on the structure-properties relationship of diphenylamine and benzothiadiazole derivatives with optoelectronic applications.