Theoretical Study of p- and n-Doping of Polythiophene- and Polypyrrole-Based Conjugated Polymers

Abstract

Density functional theory (DFT) calculations were carried out to investigate the tunable nature of band gaps of polythiophene (PTh)-and polypyrrole (PPy)-based conjugated polymers. Two series of conjugated polymers were studied as S is replaced in PTh with O, Se, and Te, and N is replaced in PPy with P, As, and Sb in the presence of Li and Cl atomic dopants. Li and Cl atoms facilitate n-type and p-type doping, respectively. Molecular and periodic calculations were carried out with a GGA functional (PBE) incorporating dispersion corrections. Narrowing band gaps or HOMO−LUMO gaps were obtained when going from O to Te in PTh analogs and P to Sb in PPy analogs. Further reduction in band gaps was observed upon doping especially in the series of PTh and analogs. A slight increase in band gaps was observed with doping in PPy analogs but the band gap is very narrow. Overall, the electronic structure of conjugated polymers can be tuned with Li and Cl atomic dopants, and this is useful in electronic device applications of conjugated polymers. Similar trends are observed for the band gaps in molecular calculations when other functionals (PBE0, B3LYP, M06) are used.

Effects of Mechanical Deformation on the Opto-Electronic Responses, Reactivity, and Performance of Conjugated Polymers: A DFT Study

“…High reactivity is observed on the nitrogen atoms, in relation to electrophiles, which is associated with the doping process of leucoemeraldine [ 107 ]. PT presents high reactivity on the sulphur atoms for both nucleophiles and electrophiles, which indicates the plausibility of p - and n -doping via this site; this is compatible with other works [ 108 , 109 ]. PPV presents high reactivity on the vinyl groups for all the reactions; this is not sensitive to stretching and can explain the well-known degradation routes of the polymer chains via varied mechanisms [ 62 , 110 , 111 , 112 ].…”

“…PPV presents high reactivity on the vinyl groups for all the reactions; this is not sensitive to stretching and can explain the well-known degradation routes of the polymer chains via varied mechanisms [ 62 , 110 , 111 , 112 ]. Finally, PPy shows high reactivity on positions 3–4 (towards electrophiles) and on position 2 (towards nucleophiles), which are compatible with the charge transfer mechanisms/doping processes proposed in the literature [ 108 , 113 , 114 ].…”

Modulating Electronic Properties of Dinitrosoarene Polymers

“…15 On the modelling side, calculations based on density functional theory (DFT) with periodic boundary conditions are being increasingly used to investigate the optoelectronic properties of OSCs. Recently, hybrid DFT and its time-dependent formulation (TD-DFT) have been employed to study periodic porphyrin nanostructures, 16 polyacenes, [17][18][19] as well as polythiophenes and polypyrroles, 20,21 exploring the changes in the band gap (Eg) and electronic structure occurring upon structural modifications, and thus identifying interesting systems and potential synthetic targets.…”

First-Principles Study on the Electronic Properties of PDPP-Based Conjugated Polymer via Density Functional Theory

“…The charge carrier density and conductivity of semiconducting CPs can be modified via p- or n-type doping (charge injection) . Through the doping process (or injection of charge carriers), appropriate impurities with desired electronic properties can be added to donate an electron to the lowest unoccupied molecular orbital (LUMO) for n-type doping or to get rid of an electron from the highest occupied molecular orbital (HOMO) for p-type doping. , In the case of injection of the charge carriers, the polymer is not doped via chemicals; instead, the polymer is oxidized or reduced by adding or withdrawing electrons, respectively. , The applications of semiconductors in various devices can be expanded by tuning the energy of the band gap to achieve tailored performance . For instance, in photovoltaic cells, a low band gap increases visible light absorption, carrier mobility, and raises the photogenerated electron–hole pair separation .…”