Bismuth oxyiodide (BiOI) is expected to be promising material for photovoltaic devices since it has good activity under the visible range. Here, we studied the annealing treatment on BiOI and its effect on the photovoltaic application. Firstly, the synthesized BiOI from Bi(NO3)3 and KI was annealed at varied temperatures (100–550 °C). The structural investigation by X-ray diffraction and Raman spectroscopy analysis was supported with morphology and optical analysis by scanning electron microscope (SEM) and UV-Visible spectroscopy. Due to the heating treatment, it could result in iodine-deficient bismuth-based materials, namely Bi7O9I3, Bi5O7I, and β-Bi2O3. Secondly, the photovoltaic test measurement was performed by solar simulator air mass (AM) 1.5 illumination which presented the current-voltage curve from each material. The enhancement of photovoltaic performance was given by the increase of temperature up to 300 °C. At that temperature, the performance of the device which consisted of Bi7O9I3 achieved three times higher efficiency than the annealed parent BiOI at 100 °C. Hence, the structural changing owing to the oxygen addition to BiOI structure had an impact on the photoelectrochemical cell. Based on this work, it is possible to attempt BiOI derivation with suitable holes and electron transport layers for better photovoltaic performance.

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A study about the angle effect on the synthesis of BiOI films via modified successive ionic layer adsorption and reaction (SILAR) and its application as p-type semiconductor in solar cell construction have been carried out. By involving the angle inclination on the BiOI synthesis process in this work, it showed the impact on the BiOI film thickness. We found the thicker films contained larger flaky morphology which was displayed by the FESEM image. Also, it exhibited an increase of the Bi-I internal stretching mode (E g ) in the Raman spectra, BiOI peak absorbance in the visible region, and its crystal intensity in the XRD pattern along with the decreasing angle from 90°to 50°while SILAR process was running. Although our BiOI films performed better J sc compared to previous studies, their photovoltaic parameters decreased slightly upon the reducing angle, which induced larger BiOI growth in the larger flaky cluster.