Shengping Ruan

Palladium diselenide (PdSe₂), a two-dimensional noble metal dichalcogenide, has recently emerged as a highly promising material for intelligent optoelectronics due to its layer-dependent bandgap tunability, high carrier mobility, and intrinsic in-plane anisotropy. However, current PdSe₂-based photodetectors are largely limited to single-pixel architectures, which fundamentally constrain their capabilities for spatially resolved sensing and on-chip information processing. In this work, we propose an in situ growth PdSe₂/Si van der Waals heterojunction photodetector array that integrates broadband photodetection, polarization imaging, and in-sensor optical computing within a unified and scalable platform. Benefiting from the strong built-in electric field at the heterointerface, the device exhibits excellent self-powered photoresponse over a broad spectral range from 375 to 1550 nm, achieving a responsivity of 203.89 mA/W and a specific detectivity of 3.3 × 10¹¹ Jones at the infrared band. Under zero-bias operating conditions, real-time optical transmission of ASCII information is successfully demonstrated at 1310 nm. In addition, benefiting from the intrinsic anisotropic absorption of PdSe₂, the heterojunction device enables polarization-resolved imaging with a decent anisotropy ratio. Leveraging on the programmable pixel biasing, edge extraction and image sharpening are directly realized within the PdSe₂/Si heterojunction array, providing a promising pathway toward in-sensor computing and integrated intelligent optoelectronic systems.

Based on a strategically designed NiO/InGaO type-II p–n heterojunction (NIH) architecture, this work presents a high-performance metal–semiconductor–metal ultraviolet photodetector (UVPD). The top-layer n-InGaO (IGO) film, featuring heavy doping-induced carrier degeneracy that positions the Fermi level near the conduction band minimum, establishes an ideal Ohmic contact with Au interdigital electrodes through efficient quantum tunneling. This configuration ensures barrier-free charge extraction and significantly augments photoconductive gain through self-trapped holes localized at abundant oxygen vacancies of IGO. Coupled with the underlying p-type NiO layer, the structure forms a p–n heterojunction that constructs a robust built-in electric field (Ebi), enabling efficient separation of photo-generated electron–hole pairs and suppressing trap-assisted recombination. Notably, this Ebi efficiently mitigates the persistent photoconductivity effect intrinsic to oxide semiconductors. Benefiting from this optimized energy band engineering and interfacial design, the fabricated NIH UVPD achieves a remarkable responsivity of 1.82 × 104 A/W and an exceptional external quantum efficiency of 8.07 × 106% at 5 V under 280 nm illumination, demonstrating great potential for high-performance UV detection.

A solar-blind metal–semiconductor–metal ultraviolet photodetector (UVPD) based on a MgZnO/InGaO (MZO/IGO) heterojunction (MIH) was fabricated. The presence of self-trapped holes in the non-bonding p-orbitals of oxygen vacancies in IGO endows it with high photoconductive gain characteristics. The built-in electric field of MIH effectively depletes the majority carriers in the dark. The Au electrode and upper IGO film form an ideal ohmic contact, enabling unimpeded carrier transport and thereby enhancing the device's photoconductive gain. The findings reveal that the MIH UVPD achieved a significant photo current of 1.88 mA and a minimal dark current of 0.21 nA at 5 V bias, resulting in an ultrahigh light-to-dark current ratio (8.95 × 106) of 6 orders of magnitude. Under the same bias, MIH UVPD exhibits a notable responsivity (R) of 1.45 × 104 A/W at 260 nm within the solar-blind region, along with a UV/visible light responsivity suppression ratio of 6.04 × 104 (R260 nm/R400 nm) and an impressive detectivity (D*) of 7.88 × 1017 Jones, suggesting its potential for fabricating high-performance solar-blind UVPDs.