Microwave-driven architectures of hierarchical polyaniline–CNT composites: unveiling structure–electrocatalysis–performance coupling for platinum-free dye-sensitized solar cells (DSSCs)

This paper reports a synthesis of hierarchical polyaniline (PANi)-carbon nanotube (CNT) composites, produced by a rapid microwave-assisted synthesis method as effective platinum-free counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). The composites were deposited directly on conductive glass substrates by maximizing the polymerization time (60 s) and CNT content (2–4 wt%). The 3% CNTs/PANi composite had the best surface area, enhanced crystallinity, and homogenous nanostructure which was confirmed by analyzing BET, XRD, and SEM. Cycles voltammetry was seen to have better electrocatalytic activity with the highest anodic current (0.22 mA at + 0.39 V) and on the cathodic current (− 0.21 mA at − 0.42 V). The electrical conductivity was 6.25 mS/cm which is higher than the electrical conductivity of pure PANi (4.3 mS/cm). DSSCs with 3% CNTs/PANi CE had power conversion efficiency (PCE) of 5.1% leading to the improved result over Pt-based (5.0%) and PANi-only (3.1%) systems. The improvement of photovoltaic performance was explained by decreased charge transfer resistance (101.86 Ω), high level of electronic transport, and more catalytic sites. Transient photoresponse measurements further confirmed accelerated charge extraction dynamics. This work underscores the strong structure–electrochemical interplay in microwave-driven PANi/CNT architectures and highlights their potential as scalable, cost-effective alternatives to platinum for high-performance DSSCs.