DFT and experimental investigation of nanostructured boron subphthalocyanine chloride-films based hybrid photodiodes: Bridging organic and inorganic materials for sustainable light detection

Abstract

This study presents a comprehensive investigation of boron subphthalocyanine chloride (B-SubPcCl), combining computational and experimental approaches to reveal its unique structural, electronic, and optoelectronic characteristics. DFT calculations at the B3LYP/SDD level reveal that the molecule adopts a non-planar geometry and exhibits a ground-state energy gap of 2.68 eV, a substantial dipole moment of 8.19 D, and a first hyperpolarizability significantly exceeding that of urea, confirming its strong nonlinear optical (NLO) potential. Complementary NBO and MEP analyses demonstrate pronounced intramolecular charge transfer and clearly defined reactive regions, emphasizing the molecule's inherent electronic versatility and suitability for advanced optoelectronic applications. Experimentally, thermally evaporated thin films exhibit uniform nanocrystalline morphology with an average grain size of 27.1 nm and low RMS roughness (∼2.8 nm), as confirmed by HRTEM and AFM. Optical studies reveal multiple band gaps (1.35, 2.24, and 2.78 eV) with broad absorption spanning UV–visible–NIR regions. The Au/B-SubPcCl/n-Si/Al heterojunction shows strong rectifying behavior with a dark rectification ratio exceeding 10³, high responsivity, and detectivity, alongside fast, stable phototransient response and a light-dependent resistance ratio above 30 at −2 V. These results establish B-SubPcCl as a highly promising material for advanced optoelectronic and NLO devices, combining computational predictions with experimental validation to highlight its novel multifunctional performance.