Annealing effects on structural and photovoltaic properties of the dip-SILAR-prepared bismuth oxyhalides (BiOI, Bi7O9I3, Bi5O7I) films

Bismuth oxyhalides are becoming a promising contender for photovoltaic applications due to its non-toxic nature and decent optical properties. This study mainly deals with clarifying the effects of phase transformations on the structure, optical, and electrical properties of BiOI thin film prepared via dip-successive ionic layer adsorption and reaction (SILAR) method at different annealing temperatures ranging from 100 to 400 degrees C. Therefore, significant phase transformations (i.e., the existence of Bi7O9I3 and Bi5O7I have been confirmed at 300 degrees C and 400 degrees C, respectively) appeared in the produced films, which were mainly due to the change of annealing temperatures. The experimental results confirmed that produced films achieved the maximum current density and efficiency and minimum current density and efficiency at 100 degrees C and 400 degrees C, respectively. Experimental results were also showed that with increasing the annealing temperature from 100 to 400 degrees C, the indirect bandgap risen from 1.77 to 2.96 eV while the crystallite size decreased from 17.62 to 12.99 nm. The energy band diagram with electrolyte explained the observed poor electrical properties during the phase transformation. Hence, this result will add positive impacts on the new information on findings for the dip-SILAR-prepared BiOI photovoltaic cells.

Automated summary

This study investigates the effects of phase transformations on the structure, optical, and electrical properties of BiOI thin film under different annealing temperatures. The results show that with increasing annealing temperature, the crystallite size decreases, the indirect bandgap increases, and significant changes in electrical properties are observed. This research provides new insights into the properties of dip-SILAR-prepared BiOI photovoltaic cells and their potential for applications in the field.