Broadband photodetector based on Co3O4/ZnO/Si double heterojunctions: A morphological and optoelectronic study

Abstract

The growing demand for efficient and cost-effective optoelectronic devices has motivated extensive research into advanced photodetector architectures. This work realizes a robust platform for broadband photodetection via architectural engineering of Co3O4/ZnO/Si double heterojunctions using facile chemical spray pyrolysis. Comprehensive materials and device characterization provides fundamental insights into the role of tailored morphology, band alignment engineering, and defect landscape in dictating device behavior. Aligned ZnO nanorods and fine-grained Co3O4 layers enable efficient light harvesting and charge transport. A triple bandgap structure stemming from the synergistic combination of the two oxides facilitates broadband spectral response from 400 to 1000 nm. Based on the optical properties, triple energy bandgap ranges have been observed, ZnO exhibits an energy bandgap ranging from 2.35 eV to 3.15 eV, while Co3O4 shows energy bandgaps in the range of 1.85 eV–2.23 eV and 1.35 eV–1.5 eV. The responsivity measurements show that Co3O4/ZnO/Si double-heterojunction device has the highest responsivity over a wide range, with distinct peaks at 480 nm and 950 nm, reaching values of 3.5 A/W and 4.5 A/W, respectively. Analysis of electrical transport characteristics and energy band diagrams elucidates the photogenerated carrier dynamics and photocurrent generation governed by strategic heterointerfaces. These fundamental insights into nanoscale interface and architecture engineering lay the foundation for custom-designing high performance metal oxide heterojunction photodetectors through facile and scalable spray pyrolysis technique.