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.