Multifunctional conjugated molecules combined with electrospun CuCoP/carbon nanofibers as a modifier of the Pt counter electrode for dye-sensitized solar cells

Abstract

Star-shaped 3,6-bis(5-(4,4′-bis(3-azidopropyl)-[1,1′:3′,1′-terphenyl]-5′-yl)-thien-2-yl)-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (DPPTPTA) is combined with electrospun bimetallic copper–cobalt phosphide decorated on carbon nanofibers (CuCoP/CNF) and used as a modified layer (DPPTPTA@CuCoP/CNF) on the platinum (Pt) coated counter electrode (CE) of dye-sensitized solar cells (DSSCs). DPPTPTA possesses ladder-like energy levels for efficient charge separation while CuCoP/CNF exhibits high electrocatalytic activity and sufficient electrical conductivity. Overall, the DPPTPTA@CuCoP/CNF heterostructure exhibits attractive performance needed for CE of DSSCs. From electrochemical analysis, it is observed that the DPPTPTA@CuCoP/CNF modified layer ensures efficient charge transfer at the CE/electrolyte interface with low charge transfer resistance. Moreover, the CE/electrolyte interface possesses a small electron recombination rate, since the modified layer has good charge separation ability. Under 1 sun (AM 1.5G, 100 mW cm⁻²) conditions, the proposed DSSC achieved a photoelectric conversion efficiency (η) of 9.50%, an open-circuit voltage (V_OC) of 827 mV, a short-circuit current density (J_SC) of 16.25 mA cm⁻², and a fill factor (FF) of 0.71. Under indoor conditions, the η value at 6000 lux (1.89 mW cm⁻²) reached 25.44%. Finally, the porous three-dimensional nanofiber structure of modified layer can ensure the long-term stability (90% retention after 3000 h). Thus, the DPPTPTA@CuCoP/CNF modified layer-based DSSC can be considered as a promising device for possible renewable energy applications.