Fabrication of Cs2AgBiBr6-based perovskite solar cells using soluti̇on-based methods under atmospheric conditions

In this study, the fabrication of the all-inorganic lead-free halide perovskite compound Cs2AgBiBr6, considered as one of the alternative materials in terms of toxicity and stability compared to organic-inorganic Pb-based perovskite compounds, was optimized in an ambient atmosphere. Three different approaches, including direct annealing, vacuum drying, and gas quenching, were used during or after the spin-coating process of this compound. Among these approaches, only gas quenching provided continuous film morphology. It has been determined that the gas flow rate affects the solvent evaporation rate and, consequently, the crystallinity, morphology, and optical properties of the perovskite films. The average grain size increased from 150 nm to 185 nm with a decrease in the gas flow rate from 18 L/min to 6 L/min. The slow gas flowing rate has led to a slower removal of the solvent, resulting in fewer nuclei formation and allowing the formed crystals to merge more evenly and slowly. Therefore, better-crystallized perovskite grains were formed. Perovskite films were utilized as the absorbing layer in the perovskite solar cells with the configuration of FTO/c-TiO2/m-TiO2/perovskite/carbon. The best-performing cell exhibited an open-circuit voltage (VOC) of 1.04 V, short-circuit current density (JSC) of 2.11 mA/cm2 a fill factor (FF) of 67.4%, and an efficiency value of 1.47%. There was no decrease in the initial efficiency after 840 hours in the room temperature shelf-life stability test of these cells. In addition, it has been observed that the cell maintained 66% of its initial efficiency after 840 hours at 65 °C. As a result of this study, it has been determined that, although the efficiency of Cs2AgBiBr6-based perovskite solar cells is lower than that of traditional organic-inorganic-based cells, the stability of Cs2AgBiBr6 is better than traditional perovskites in ambient atmosphere. Furthermore, it has been concluded that the gas quenching method is one of the most ideal approaches for the development of all-inorganic perovskite solar cells under ambient conditions.