Multilayer photoactive nanocolloidal PPy:PSS as a novel substitute for Pt free counter electrode in DSSC

Abstract

Water dispersible and highly processable, Polypyrrole (PPy) nanocolloidal particles were synthesized by chemical oxidation polymerization with 15 wt % of anionic polyelectrolyte poly(styrene sulfonate) (PSS) at 58C has been reported in this work. This polymer composite (PPy:PSS) was competent with conventional Pt counter electrode (CE) when compared for dye sensitized solar cells (DSSCs). Morphological analysis revealed smooth and spherical shaped nanoparticles of PPy. Interaction between the SO 3 H groups and Py units in PPy improved the thermal stability of PPy with higher doping levels of PSS. The nanocolloidal solution was spin coated at 4000 rpm. The layer by layer, self-assembled multilayer thin films were used as CE in DSSCs. There was a linear dependence of DSSCs performance with film roughness for the self-assembled multilayer PPy:PSS films. Single layer films showed better electrocatalytic behavior than multilayer films. All the PPy:PSS films had good electrochemical stability. The DSSC efficiency of 3.40% was observed for chemically oxidized PPy with 15 wt % PSS for single layer film, with a highest FF of 0.7154. The low cost, good performance, rapid and simple fabrication method of PPy:PSS composite modified CE could be a potential alternative for Pt in the DSSCs.

Effect of CuBr2salt treatment on the performance of nanocolloidal PPy:PSS multilayer thin film counter electrodes of dye‐sensitized solar cells

“…Also, the presence of an excess amount of bulky and hydrophobic anionic PSS surfactant affected the electrocatalytic activity and created higher charge-transfer resistance (R ct ), leading to relatively poor performance. 52 This is in accordance with the obtained EIS results. Thus, with CuBr 2 treatment on multilayer PPy:PSS films, we were able to demonstrate that the R ct can be altered in the electrolyte/electrode interface.…”

“…51 The evolution of PPy:PSS film roughness is consistent with the film growth behavior, which is due to the tendency of PPy:PSS polyelectrolyte to be a colloidal dispersion in aqueous medium. 52…”

“…One possible reason is that a higher wt % of PSS not only dispersed in the PPy matrix but also tends to aggregate on the surface of PPy. 52 Hence, during 1 M CuBr 2 salt treatment, more Cu 21 ions will be attached to the PPy matrix along with PSS, which would be a hindrance for the contact between the PPy matrix and the I 2 3 electrolyte. Chen et al notably reported 37 that the excess PSS with SO 2 3 groups in the PPy matrix would cause a high degree of distortion in the conjugated PPy segments as a result of steric congestion.…”

CuBr2‐induced charge screening on photoactive nanocolloidal polypyrrole:poly(styrene sulfonate) composite multilayer thin‐film counter electrodes for high‐efficiency dye‐sensitized solar cells

“…The R ct values of the PPyCB films are decreased, due to the increasing surface area of the polymer films with the number of (one, three and five) bilayers, which is attributed to the elimination of a few PSS anions during the salt treatment. This trend is reversed in the PPyUt films due to the presence of excess PSS, which not only disperses in the PPy matrix, but tends to aggregate on the surface of PPy . Moreover, for the PPyUt films the higher value of R ct2 is due to some perturbation in electrolyte diffusion, which influences the impedance behaviour of the films in the low‐frequency region .…”

“…Moreover, the lower magnitude of cathodic current density of the PPyUt films is because PSS counterion hinders polymer–polymer interchain interaction, thereby decreasing the nominal effective conjugation length for exciton/electron migration. This significantly harms the conductive paths of PPy and reduces the reduction ability of the electrolyte . The increasing propensity of peak current for the PPyCB films indicates the presence of a larger number of active sites for electrocatalytic reactions, which is not found in the PPyUt films.…”