Tuning the degree of oxidation and electron delocalization of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) with solid-electrolyte

Abstract

We report on the effects of ionic interaction on the electronic structure of PEDOT:PSS where the oxidation state of PEDOT is an import aspect for various applications. Additional ionic interactions are introduced and controlled by varying the fraction of poly(ethylene oxide) (PEO). These interactions are balanced against the inherent cohesive forces within each of the polymers constituting intertwined networks. Raman spectra evidenced a peak-shift as high as ∼14 cm −1 for C C vibrational region which suggested increasing degree of oxidation of PEDOT for higher PEO fractions. Changes to the single and bipolaronic absorption bands support the results from the Raman spectra. For highest PEO fraction neutral-PEDOT and lowered bipolaron density is attributed to localization of PEDOT chains within PEO matrix. Interestingly, for higher PEO fractions the electronic density of states (DOS) of HOMO and core-levels (S2p, C1s and O1s) suggested increased degree of oxidation and electron localization on PEDOT. Near and below (∼12 eV) Fermi level, contribution to the O2p and C2p atomic orbitals depicted significantly different DOS. Also we note energetic shift for O2s/C2s and bonding CC atomic and molecular DOS, respectively. The correlation between some surface and bulk-related properties suggests the uniformity of the blend material which might be vital for the application in electrochemical devices.

Graphene oxide-doped PEDOT:PSS as hole transport layer in inverted bulk heterojunction solar cell

“…In the case of GO/PEDOT:PSS system, we expect that the density of polaron and bipolaron species in PEDOT:PSS change [21]. By given the nature of interaction between GO and PEDOT:PSS [21,48], we also speculate that the effect of doping may be limited to the highest occupied molecular orbital (HOMO) edge or close to the Fermi energy. Essentially, O2p and mixed state of O2p/C2p of PEDOT are effected that may play a direct role in the transport properties and hence the device efficiency.…”

“…While the differences in the viscosity of PEDOT:PSS solutions would influence the formation of the film and hence the nature and efficiency of electron transport. Also, the mode of synthesis [32,33] of GO greatly modifies the functional groups and their density at the surface of graphene [21,34]. This in turn changes the degree of doping of PEDOT:PSS, however, the nature of fundamental interaction still remains as we discussed in the previous sections.…”

“…In other words, the fraction of PSS at the surface of the films has decreased after GO doping. Accumulation of PSS at the surface of PEDOT:PSS films is inevitable due to the Coulombic effects [21,38,39].…”

“…The secondary doping helps in phase separation and thus the formation of large PEDOT domains. The dopants such as metal oxides [18], solvents [19,20], solid electrolytes [21], ionic liquids [22], surfactants [23] etc are employed as secondary dopants. Apart from these recently graphene oxide (GO) has been employed as a secondary dopant in PEDOT:PSS.…”

Improvement to the thermoelectric properties of PEDOT:PSS

“…As observed for all experimental chapters, this technique was utilized to measure the chemical shifts of Sulphur 2p peaks in order to study the reduction of thiophene carriers whereby a shift towards lower binding energy infers reduced carrier concentration. 308 This was instrumental in also determining the oxidation state of other species such as Nitrogen via the position of the BE for Nitrogen 1s. 295 For the peak fitting the software freely available CASA XPS (http://www.casaxps.com/) was used to model the high resolution XPS data.…”