Annealing effects on structural and photovoltaic properties of the dip‑SILAR‑prepared bismuth oxyhalides (BiOI, Bi_7O_9I_3, Bi_5O_7I) films

摘要

Bismuth oxyhalides are becoming a promising contender for photovoltaic applications due to its non-toxic nature anddecent 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 °C. Therefore, significant phase transformations (i.e.,the existence of Bi7O9I3and Bi_5O_7Ihave been confirmed at 300 °C and 400 °C, respectively) appeared in the producedfilms, which were mainly due to the change of annealing temperatures. The experimental results confirmed that producedfilms achieved the maximum current density and efficiency and minimum current density and efficiency at 100 °C and400 °C, respectively. Experimental results were also showed that with increasing the annealing temperature from 100 to400 °C, the indirect bandgap risen from 1.77 to 2.96 eV while the crystallite size decreased from 17.62 to 12.99 nm. Theenergy 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 BiOIphotovoltaic cells.