Layer assembled polyaniline and CuWO₄ film as Pt-free efficient counter electrodes of dye-sensitized solar cells

The development of transition metal compounds (TMCs) and conductive polymers composite catalysts substitute for the traditional scarce Pt-based catalysts of counter electrodes (CEs) has been recognized as one of the distinguishing paths to enhance power conversion efficiency (PCE) and decrease manufacturing costs of dyesensitized solar cells (DSSCs). At present, various thin film preparations have been developed and applied to prepare assortment CEs. Herein, both polyaniline (PANI) and CuWO4 film were prepared, and further to fabricate layer-by-layer composite CEs of CuWO4/PANI, PANI/CuWO4, CuWO4/PANI/CuWO4, PANI/CuWO4/PANI, aiming to promote the charge transfer capability and thus improve catalytic activity. And then, PANI, CuWO4 and four composite layered CEs obtained PCE values of 5.14, 5.64, 5.96, 6.21, 4.96 and 4.24% toward the regeneration of I-3(-) /I- redox couples in the assembled DSSCs, respectively. Particularly, the fascinating performance of the bilayer PANI/CuWO4 CEs inherits the excellent electrical conductivity and the abundant porous structure of PANI skeletons for effective electrolyte diffusion. Meanwhile, the CuWO4 layer was coupled to the layers of PANI by thermal activation annealing treatment to furnish rich inner active sites for the regeneration of I-3(-) /I- couples. Benefit from the synergistic effects of PANI and CuWO4, the as-prepared PANI/CuWO4 CEs manifests the highest PCE of 6.21%, indicating an inspiring strategy by the layered assembly Pt-free CEs with the cost effective and high-performance as an alternative Pt-based catalyst for DSSC.