Synthesis and Photoelectric Properties of D-A Conjugated Polymers of Benzothiadiazoles with Different Molecular Weights

Abstract

In this work, we have synthesized and characterized a series of Donor−Acceptor (D–A) conjugated polymers (PffBT4T-2DT) with different molecular weights, introduced a microwave method into the synthesis process, shortened the experimental cycle time by over 5 days and increased the molecular weight of the polymers. The conditions affecting the molecular weight of the polymers were investigated. It is shown that the prepared conjugated polymers have excellent thermal stability and solubility, higher molecular weight polymers have broader absorption spectra and stronger inter-chain aggregation, and the strong aggregation ability of polymer chains is dependent on molecular weight and solution temperature, with lower polymer molecular weight and higher solution temperature both causing weaker polymer chain aggregation. The polymer films of the three molecular weights have a uniform surface with a roughness of about 0.83 and good crystallinity. Transistor test results show that the higher molecular weight polymers perform better when applied to field effect transistors, with mobilities as high as 0.124 cm² V⁻¹ s⁻¹ and threshold voltages as low as 2 V.

Graphical Abstract

A series of donor-acceptor conjugated polymers (PffBT4T-2DT) with different molecular weights were synthesized by introducing the microwave method. The thermodynamic, optical, electrochemical and photovoltaic properties of the polymers were characterized, and the effect of molecular weight on the performance of organic field effect transistors (OFETs) was investigated.