Enhanced Photovoltaic Performance of Poly(3,4-Ethylenedioxythiophene)Poly(N-Alkylcarbazole) Copolymer-Based Counter Electrode in Dye-Sensitized Solar Cells

Conducting polymers are emerging as promising alternatives to rare and expensive platinum for counter electrodes in dye-sensitized solar cells; due to their ease of synthesis, they can be chemically tuned and are suitable for roll-to-roll production. Among these, poly (3,4-ethylenedioxythiophene) (PEDOT)-based counter electrodes have shown leading photovoltaic performance. However, certain conductivity issues remain that affect the effectiveness of these counter electrodes. In this study, we present an electropolymerized PEDOT and poly(<i>N</i>-alkylated-carbazole) copolymer as an efficient electrocatalyst for the reduction in I3- in dye-sensitized solar cells. Copolymerization with <i>N</i>-alkylated carbazoles significantly increases the conductivity of the polymer film and facilitates rapid charge transport at the interface between the polymer electrode and the electrolyte. The length of the alkyl substituents also plays a crucial role in this improvement. Electrochemical analysis showed a reduction in charge transport resistance from 3.31 Ω·cm² for PEDOT to 2.26 Ω·cm² for the PEDOT:poly(<i>N</i>-octylcarbazole) copolymer, which is almost half the resistance of a platinum-based counter electrode (4.12 Ω·cm²). Photovoltaic measurements showed that the solar cell with the PEDOT:poly(<i>N</i>-octylcarbazole) counter electrode achieved an efficiency of 8.88%, outperforming both PEDOT (7.90%) and platinum-based devices (7.57%).