Polarons, bipolarons, and solitons in conducting polymers

Theoretical Modeling of the Doping Process in Polypyrrole by Calculating UV/Vis Absorption Spectra of Neutral and Charged Oligomers

“…16,22 Other experiments were shown to be in agreement with preference for polaron formation, 17,23,24,102 energetic degeneracy between polarons and bipolarons, 25 and coexistence of polarons and bipolarons. 26 Theoretically bipolaron formation was promoted by Bredas et al, 9,20 who calculated a bipolaron binding energy of 0.45 eV for polypyrrole with the tight binding method. 58 The driving force for recombination of polarons and overcoming the Coulomb repulsion between two positively charged defects is gain in lattice relaxation energy when the two charges are coupled to the same lattice mode.…”

“…12,13,[16][17][18] The sub-band transitions of doped COPs were rationalized originally in terms of bipolaron formation since there is no correlation between ESR signals and conductivity. 9,[19][20][21][22] Preference for bipolarons has been questioned by some experimentalists from the start, 17,18,[23][24][25][26] but others rationalized their observations in terms of bipolarons. 13,16,22 Especially after the doping behavior of monodisperse polyenes [27][28][29] and oligothiophenes (OTs) [30][31][32][33][34][35][36][37][38][39][40][41] was investigated in solution, the bipolaron model was challenged.…”

Physical electrochemistry of nanostructured devices

“…If two charge carriers share the same molecular deformation a bipolaron (B) is formed; the energy gained by forming only one deformation may outweigh the increased Coulomb repulsion energy. 97 It has been pointed out that the relative stability of one B versus two P may depend on the experimental conditions such as solvent and type of counterions. 98 The statistics of P and B in conjugated polymers are well known, 99,100 and from these expressions the chemical capacitance can be calculated.…”

Theoretical Investigation of Excited States of Oligothiophene Anions

“…6 Both levels were assumed to be unoccupied (bipolaron formation) because three transitions were expected if one level were occupied (polaron formation). [13][14][15][16][17] That the two intragap levels are placed symmetrically was rationalized by a small interaction of the sulfur atom with the conjugated backbone. 6 For n-doped PT, both intragap levels are occupied.…”

“…Electron-hole symmetry was confirmed experimentally for didodecylsexithiophene, which forms stable mono-and dications and anions. 19 In contrast to the predictions based on the polaron-bipolaron model (Scheme 1), [13][14][15][16][17] experimental doping studies of oligothiophenes (OTs) in solution [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] showed that monocations (polarons) are associated with two sub-band transitions, while dications (bipolarons) give rise to only one sub-band feature. This was confirmed with theoretical investigations at various semiempirical [36][37][38][39] and ab initio levels, 34,40 and with density functional theory (DFT).…”