Layered bismuth triiodide (BiI3) is a 2D material that has emerged as an ideal choice for optical sensors. Although BiI3 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 BiI3 material thin films for photodetection applications. The structural, optical, and morphological study of BiI3 thin films prepared at 3000-6000 rpm were investigated. XRD analysis indicates formation of BiI3 films and revealed that BiI3 has a rhombohedral crystal structure. FESEM analysis showed that BiI3 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 BiI3 particles. The UV spectroscopy and photoluminescence analysis revealed that BiI3 films strongly absorb light in the visible region of spectra with a high absorption coefficient of ∼104 cm-1, have an optical band gap of ∼1.51 eV. A photodetector was realised using fabricated BiI3 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 × 106 Jones at a bias voltage of 0 V. Our results point towards a new direction for layered 2D BiI3 materials for the application in self-biased photodetectors.
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