Target-Induced Tandem Built-In Electric Fields in the Hollow SnS ₂ /ZIS@ZnS Heterojunction for the Photoelectrochemical Immunoassay

/ZIS@ZnS. Owing to the inherent differences in work function among these three heterocomponents, a tandem BIEF was established within the heterojunction. The tandem BIEF effectively facilitated charge transfer and enhanced the photoelectric conversion efficiency, ultimately enhancing the photocurrent signal. Benefiting from the pronounced variation in photocurrent, the proposed PEC sensing platform enables highly sensitive detection of CEA, exhibiting a linear detection range from 0.02 to 50 ng/mL with a detection limit as low as 3.5 pg/mL. This work provides a promising avenue to develop a high-performance PEC sensing platform based on BIEF as a signal modulation mechanism for clinical diagnostics.