Three random copolymers PE- co -M1 , PE- co -M2 , and PE- co -M3 were obtained by electrochemical polymerization of donor–acceptor–donor monomers M1 , M2 , and M3 with 3,4-ethylenedioxythiophene moiety, respectively, using a 1:1 molar ratio of the corresponding monomers, to find new properties and a more effective way to control the optoelectronic properties in conjugated system. For comparison purpose, polymers P1 , P2 , and P3 were prepared from the corresponding monomer units M1 – M3 , respectively, by electrochemical polymerization. We also present efficient synthesis, characterization, and comparative density functional theory (DFT) calculations of the monomers M1 – M3 and polymers P1 – P3 . Cyclic voltammetry, spectroelectrochemistry, and electrochromic properties of all of the polymers P1 – P3 and copolymers PE- co -M1 , PE- co -M2 , and PE- co -M3 were carried out and a throughout comparison was made. We have shown that electrochemical copolymerization is a powerful strategy to tune the highest occupied molecular orbital energy level, band gap, and color of the copolymer. Thus, this finding clearly indicates that the copolymers show significantly different optoelectronic properties compared to their constituent polymers.

Significant efforts have been devoted to the synthesis of conjugated molecules due to their interesting properties for organic electronic applications, it is surprising that very few studies have been reported on the development of small molecules for hole transport material (HTM) in organic solar cells through direct C−H arylation. In this work, we have studied the reaction conditions used for the facile synthesis of a series of π conjugated small molecules through direct C−H arylation. The reaction condition was optimized by using different solvents, bases and ligands to achieve the maximum possible yield. Ten phenyl(s)‐flanked conjugated small molecules were prepared using the optimized reaction condition and were characterized. Density functional theory was studied on these molecules to understand the structure‐property relationship and predicting the reliable geometry, electronic structure and properties of conjugated systems. Electrical and optical properties were measured by cyclic voltammetry and UV‐vis absorption spectroscopy. Finally, the organic solar cells were fabricated by solution‐processable deposition of these HTM with device geometry of ITO/HTM/PCDTBT:PC70BM/Al and achieved a power conversion efficiency of 2.40 % under ambient conditions. This method has the advantages of using different aromaticity of heterocyclic rings combined with conjugation length and electronegativity of heteroatom(s) to allow fine‐tuning of HOMO level and band gap engineering.

No abstract

No abstract

We present systematic opto-electrochemical studies of D–A polymer films prepared using different electrolytes and solvents. Significant effects of both the factors on the optical, electrochemical, morphology and electrochromic properties were found.