Broadband Flexible Photodetectors Based on CdS_xSe_1–x/PbI₂ Heterojunctions

2D photodetectors can considerably outperform their Si counterparts and thus appear promising for contemporary optoelectronic circuits. However, limited charge separation efficiency and poor optical absorption make it complicated to create ultrasensitive broad response photodetectors using a single 2D material. While hybrid heterostructures combining 2D and 1D materials could be a promising solution, previously used binary/binary 1D/2D photodetectors have a performance that is merely satisfactory at best. To address these limitations, here we for the first time demonstrate vertically stacked ternary/binary photodetectors (VPDs) based on 1D ternary CdS x Se 1– x nanoribbon (NR)/2D binary PbI 2 nanosheets (NS) heterostructures. While excellent crystallinity of the ternary/binary structure enables efficient carrier transport, a type-II heterojunction at the interfaces facilitates charge separation. As a result, our devices exhibit excellent photodetection ability in broad range with superior photoresponsivity (567 A/W), photosensitivity (1.60 × 10 7 %), specific detectivity (1.96 × 10 15 Jones), external quantum efficiency (1.17 × 10 5 %), and the response speed which is several orders of magnitude higher as compared to our reference devices based on PbI 2 NS and most of the previously reported photodetectors in visible range. Furthermore, our VPDs fabricated on flexible substrates show stable operation after being subjected to multiple bending cycles and retain excellent performance following several weeks of storage in an air environment. Our results provide advanced insights into the design and fabrication of environmentally stable flexible VPDs for future optoelectronics circuits.