Self-biased photodetector using 2D layered bismuth triiodide (BiI 3 ) prepared using the spin coating method.

Layered bismuth triiodide (BiI ₃ ) is a 2D material that has emerged as an ideal choice for optical sensors. Although BiI ₃ has been prepared using vacuum-based deposition techniques, there is a dearth of research studies on synthesizing this material using chemical route. The present work uses a facile spin coating method with varying rotation speeds (rpm) to fabricate BiI ₃ material thin films for photodetection applications. The structural, optical, and morphological study of BiI ₃ thin films prepared at 3000-6000 rpm were investigated. XRD analysis indicates formation of BiI ₃ films and revealed that BiI ₃ has a rhombohedral crystal structure. FESEM analysis showed that BiI ₃ films prepared at different rpm are homogeneous, dense, and free from cracks, flaws, and protrusions. In addition, films show an island-like morphology with grain boundaries having different grain sizes, micro gaps, and the evolution of the granular morphology of BiI ₃ particles. The UV spectroscopy and photoluminescence analysis revealed that BiI ₃ films strongly absorb light in the visible region of spectra with a high absorption coefficient of ∼10 ⁴ cm ^-1 , have an optical band gap of ∼1.51 eV. A photodetector was realised using fabricated BiI ₃ film obtained at an optimum spin speed of 4000 rpm. It showed rapid rise and decay times of 0.4 s and 0.5 s, a responsivity of ∼100 μA W ^-1 , external quantum efficiency of 2.1 × 10 ^-4 %, and detectivity of ∼3.69 × 10 ⁶ Jones at a bias voltage of 0 V. Our results point towards a new direction for layered 2D BiI ₃ materials for the application in self-biased photodetectors.
Competing Interests: There are no conflicts to declare.
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