A ~70% improvement in power conversion efficiency (PCE, η) is observed for the devices fabricated with a binary hybrid composite of graphitic carbon nitride and zinc oxide nanorod, i.e., (g-C3N4-ZnO NR) [η ≈2.43%, for an optimized weight ratio (0.5:1)] as compared to the pristine ZnO NR device (η ≈0.65%). Systematic investigations reveal that g-C3N4 boosts light harvesting ability of the photovoltaic devices primarily by impeding photo-induced electron interception to the redox couple and injecting population to the conduction band of semiconductor. Electrochemical impedance spectroscopy (EIS) analysis shows a reduced tunneling of photo-induced electrons to the sulfide-polysulfide (S2-/Sn2-) redox shuttle in case of (g-C3N4-ZnO NR) composite devices. Higher recombination resistance (Rk) indicates that the g-C3N4 sheet act as a barrier for photoinduced electron interception at the working electrode/electrolyte interface. Preliminary investigation using steady state and dynamic photoluminescence analyses suggests a similar fact about the photo-induced electron injection from g-C3N4 sheets to ZnO, contributing to the enhanced light harvesting ability of (g-C3N4-ZnO NR) composite devices.