Design, Synthesis, and Investigation of the Photodiode Performance of a Novel D–π–A–π–D-Type Organic Semiconductor Based on Dibenzosuberenone with Anthracenyl Donors

Abstract

Organic photodiodes based on donor–π–acceptor (D–π–A) molecular architectures have attracted significant attention owing to their tunable optoelectronic properties, solution-processability, and potential for low-cost photodetection applications. However, despite the remarkable photophysical characteristics of dibenzosuberenone derivatives, studies investigating anthracene-functionalized dibenzosuberenone-based D–π–A–π–D systems for photodiode applications remain very limited in the literature. In this study, a novel π-conjugated organic semiconductor (BADA) possessing a D–π–A–π–D architecture was rationally designed and synthesized starting from dibenzosuberone through multistep aromatic functionalization and Sonogashira coupling reactions. The resulting molecule consists of anthracenyl donor units, linear ethynyl π-bridges, and a dibenzosuberenone acceptor core, providing an extended delocalized electronic framework. Subsequently, an Au/BADA/p-Si/Al Schottky-type photodiode was fabricated by spin-coating the BADA interfacial layer onto p-type silicon followed by thermal evaporation of Au and Al contacts. The electrical and photoresponse characteristics of the fabricated device were systematically investigated under illumination intensities ranging from 20 to 100 mW/cm². The ideality factor (n) increased from 1.74 in the dark to 3.96 under illumination, while the barrier height (Φ_b) decreased from 0.76 eV to 0.57 eV, indicating illumination-induced barrier modulation effects. The photocurrent exhibited a power-law dependence on light intensity with an exponent of m = 1.10, revealing nearly linear and slightly super-linear behavior. The responsivity (R) was found to vary between 1.46 × 10⁻⁶ and 1.60 × 10⁻⁶A/W, while the specific detectivity (D^*) ranged from 7.9 × 10⁷ to 9.3 × 10⁷ Jones within the investigated illumination range. The photosensitivity increased monotonically, reaching approximately 15 at 100 mW/cm². The obtained results demonstrate that the Au/BADA/p-Si/Al structure exhibits stable and reproducible photoresponse characteristics and represents a promising candidate for organic photodetector applications.