Investigation of stability for Cs₂TiBr₆ perovskite materials exposed to air environment

Abstract

Lead-free all-inorganic Cs2TiBr6 perovskite solar cells have attracted attention with their 3.3% efficiency and stability. However, instability in air ambiance has been reported for Cs2TiBr6 synthesized in powder form. In this work, Cs2TiBr6 perovskite is synthesized using a solution-based method. Time-dependent X-ray diffraction patterns are analyzed for air ambience. Cs2TiBr6 perovskite quickly deteriorates and decomposes in the air. Morphology and optical properties are obtained using a scanning electron microscope and the ultraviolet region, respectively. The average particle size is ~2.4 µm. The forbidden band gap is found to be 1.82 eV from the Tauc plot. The Hall Effect measurement of the perovskite pellet is taken at room temperature and under vacuum. The pellet has high resistance (1.1×104 ohm·cm) and high Hall mobility (502 cm2V-1s-1). Cs2TiBr6 shows p-type conductivity. Low stability to air and high resistance are handicaps for the Cs2TiBr6 perovskite absorber layer in solar cell applications.