Self-biased photodetector using 2D layered bismuth triiodide (BiI₃) prepared using the spin coating method

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Layered bismuth triiodide (BiI₃) is a promising 2D material for optical sensors.
• Existing synthesis methods for BiI₃ primarily rely on vacuum-based deposition.
• There is a need for scalable and cost-effective chemical synthesis routes for BiI₃.

Purpose of the Study:

• To develop a facile chemical route for fabricating BiI₃ thin films using spin coating.
• To investigate the structural, optical, and morphological properties of spin-coated BiI₃ films.
• To fabricate and characterize a photodetector based on the synthesized BiI₃ thin films.

Main Methods:

• Thin films of BiI₃ were prepared using spin coating at varying rotation speeds (3000-6000 rpm).
• Structural characterization was performed using X-ray Diffraction (XRD).
• Morphological analysis was conducted using Field Emission Scanning Electron Microscopy (FESEM).
• Optical properties were studied using UV-Vis spectroscopy and photoluminescence.
• A photodetector device was fabricated and its performance was evaluated.

Main Results:

• XRD confirmed the formation of BiI₃ with a rhombohedral crystal structure.
• FESEM revealed homogeneous, dense, and crack-free BiI₃ films with island-like morphology.
• BiI₃ films exhibited strong visible light absorption (∼10⁴ cm^-1) and an optical band gap of ∼1.51 eV.
• The optimized photodetector (4000 rpm) showed rapid response times (0.4 s rise, 0.5 s decay), responsivity of ∼100 μA W^-1, EQE of 2.1 × 10^-4%, and detectivity of ∼3.69 × 10⁶ Jones at 0 V bias.

Conclusions:

• A facile spin coating method enables the synthesis of high-quality 2D BiI₃ thin films.
• The fabricated BiI₃ films possess excellent optical and morphological properties suitable for photodetection.
• The developed BiI₃-based photodetector demonstrates efficient performance, particularly for self-biased applications.