Abstract
<title>Abstract</title> <p> In this study, a novel organic interfacial layer based on <bold/> 1,4-dimethyl-7-isopropylazulene (Guaiazulene; <bold/> GA) was introduced into a silicon-based Schottky photodiode to fabricate an Au/GA/p-Si/Al device, and its structural, optical, electrical, and photodetection properties were systematically investigated. The GA thin film was deposited onto p-Si by spin coating, followed by thermal evaporation of Au and Al contacts. Structural characterization by XRD revealed that the GA thin film retained its crystalline framework while exhibiting reduced crystallinity and nanoscale domain formation after deposition. SEM and TEM analyses confirmed a particle-dominated heterogeneous morphology with aggregated spherical domains. Optical studies demonstrated strong UV absorption behavior, a direct optical band gap of approximately 3.56 eV. UPS measurements revealed favorable energy level alignment of the GA layer for interfacial charge transport modulation. Electrical measurements showed clear rectifying Schottky behavior under both dark and illuminated conditions. Under increasing illumination intensity (20–100 mW cm⁻²), the barrier height decreased from 0.80 eV <bold/> to 0.67 eV <bold>,</bold> while the ideality factor increased from 1.24to 2.31, indicating illumination-induced interface effects and non-ideal transport processes. The photodiode exhibited strong photoresponse with a nearly linear photocurrent dependence on illumination intensity (α ≈ 1.1), confirming efficient photocarrier generation. At 100 mW cm⁻², the device achieved a photosensitivity of approximately 88, responsivity of 0.07 A W⁻¹, and specific detectivity of 2 × 10¹¹ Jones <bold>.</bold> The device also demonstrated rapid switching behavior with rise and decay times of approximately 0.1 s, excellent ON/OFF reproducibility, broad spectral sensitivity (365 nm, 395 nm, and 850 nm), and stable performance after 30 days of storage. These results demonstrate that the GA interfacial layer effectively enhances junction properties and photodetection performance. The fabricated Au/GA/p-Si/Al photodiode shows strong potential for low-cost, high-performance, and UV-sensitive optoelectronic applications. </p>