Abstract
Fluorine-doped tin oxide (FTO) electrodes modified with polymeric films of poly 2,2 bithiophene (PBth) and/or poly 2,2’,5,2’’-terthiophene (PTerth) were subjected to optical, photoelectrochemical (PEC), and electrochemical impedance spectroscopy (EIS) studies. Electropolymerization of mixed monomers containing bi-thiophene (Bth) and ter-thiophene (Terth) with different ratios resulted in the formation of intermixed phases. The recorded optical and PEC and EIS outcome data show that these intermixed polymer networks do not follow a monotonic relationship with the monomer ratios used to generate them. Optical studies indicate the formation of indirect and direct band gaps in the intermixed phases. Films generated in mixed monomers have greater energy-band tails than those generated from pure monomers. PEC studies indicated that these intermixed phases possess p-p type hole accumulations, evident from the initial sharp rise in photocurrent. EIS results did not support linear relationship between the percent of Bth in monomer mixture and the dielectric-related properties such as barrier energy Wm, hopping frequency (ω hopping), electrical conductivity (σ), and density of state at Fermi level N (EF).
Highlights
Many π-conjugated conducting polymers can be photoactive
Fluorine-doped tin oxide (FTO) electrodes modified with polymeric films of poly 2,2 bithiophene (PBth) and/or poly 2,2’,5,2’’-terthiophene (PTerth) were subjected to optical, photoelectrochemical (PEC), and electrochemical impedance spectroscopy (EIS) studies
The recorded optical and PEC and EIS outcome data show that these intermixed polymer networks do not follow a monotonic relationship with the monomer ratios used to generate them
Summary
Several studies were conducted to decipher the reason(s) behind the photoactivties (Bard 1979, Grrett et al 1955), Holmes 1961, Oyama 1989, Causa et al 2016, Mohammed, et al 2008, Yen Wei et al 1991, Kolodziejczyk et al 2014) Factors such as the influence of chain length on energy gaps, orbital energies, ionization potential (IP), and electron affinity (EA) were taken into consideration. Electropolymerization of mixed monomers containing two or three identical heterocyclic rings (e.g bithiophene and ter-thiophene), or di-functional heterocyclic rings can lead to formation of intermixed phases These phases can affect long-range charge separation and the chance for delocalization into such intermixed network. We studied the electro-polymerization of mixed monomers containing bi-thiophene (Bth) and ter-thiophene (Terth), to determine how the formation of intermixed phases of the produced polymers’ mix can affect optical, dielectric properties, and the photoelectrochemical outcome of these mixed polymer networks
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