<p>Ochratoxin A (OTA) is one of the most hazardous mycotoxins commonly found in crops and agricultural environments, necessitating sensitive detection methods. This study presents a photoelectrochemical (PEC) biosensor designed for OTA detection, utilizing a CdTe quantum dots (QDs) sensitized CuInS₂/NiTiO₃ heterojunction. The CuInS₂/NiTiO₃ composite was prepared by in-situ growth, and detailed characterization confirmed its structure as a Z-scheme heterojunction, allowing a significantly enhanced PEC response. To construct the biosensing interface, double-stranded DNA containing CdTe QDs-labeled complementary DNA (cDNA-CdTe QDs) was anchored on gold nanoparticles modified CuInS₂/NiTiO₃. The sensing mechanism relies on the specific binding of OTA to aptamer, which triggers the release of cDNA-CdTe QDs from the interface, thereby diminishing the sensitization of CdTe QDs and resulting in a reduced photocurrent. The developed PEC biosensor provides a linear range of 1.0 × 10⁻¹ to 5.0 × 10² pg mL⁻¹ and achieves an impressive detection limit of 0.02 pg mL⁻¹ for OTA detection. Moreover, it shows high selectivity and stability, with successful applications confirmed in the analysis of corn and soil samples. This work develops a cutting-edge approach to high-performance PEC biosensor fabrication and advances the application of PEC methods in the agricultural sector.</p> Graphical abstract <p></p>