Herein, a new label-free and blocker-free photoelectrochemical (PEC) sensor based on bifunctional CC-DEVD-peptide modified nitrogen-doped porous carbon-ZnO nanopolyhedra/CdS hybrids is developed for highly sensitive caspase-3 assay. The developed PEC sensor shows a low detection limit of about 0.14 ng mL-1 and has promising applications in the apoptosis-associated study.