Fig. 1. Refined crystal structure of Cs₂AgBiBr₆ (Cs⁺ ions are shown as big gray spheres, bromine ions as other small spheres, while Ag and Bi centered octahedra are shown as dark and light colour polyhedra, respectively)^[37]

Fig. 2. Current density-voltage (J-V) curves of a solar cell^[66]

Fig. 3. Schematic diagram of Cs₂AgBiBr₆ single crystal growth by hydrothermal reaction process^［79］

Fig. 4. Isostatic-pressing method to prepare Cs₂AgBiBr₆ wafers^[80]. (a) Schematic illustration of isostatic-pressing process; (b) as-prepared Cs₂AgBiBr₆ wafers with tunable sizes and diameters are 5, 3, and 1 cm from left to right; (c) top-down SEM image of wafer; (d) cross-sectional SEM image of wafer and inset is a higher resolution image, demonstrating grain size is larger than 100 μm

Fig. 5. Fabrication and SEM images of Cs₂AgBiBr₆ film^[88]. (a) Image of Cs₂AgBiBr₆ powder (left) and solution in DMSO (right); (b) film fabrication process diagram; SEM images of films obtained by (c) TA and (d) LPA process. Inset: film photograph with size of 25 mm×25 mm

Fig. 6. Cs₂AgBiBr₆ films with cubic double perovskite structure fabricated by capillary-assisted dip-coating (CDC) method^[92]

Fig. 7. Scheme of sequential vapor deposition processing^[46]

Fig. 8. Schematic of Cs₂AgBiBr₆ film preparation using single source vapor deposition method^[97]

Fig. 9. Synthesis of Cs₂AgBiX₆ nanocrystals^[99]

Fig. 10. Thermal injection and anti-solvent recrystallization for colloidal synthesis of Cs₂AgBiBr₆ double perovskite NCs^[47]

Fig. 11. Structure of solar cell^[1]. (a) Schematic of n-i-p architecture; (b) schematic of p-i-n architecture

Fig. 12. Current density-voltage (J-V) curves of forward and reverse scan directions^[45]

Fig. 13. Current density-voltage (J-V) curves of forward and reverse scans directions after adding anti-solvent^[105]

Fig. 14. Band gap evolution of Cs₂AgBiBr₆ crystal at high pressure and representative optical micrographs^[117]

Fig. 15. Current density-voltage (J-V) curves of forward (broken lines) and reverse (solid lines) scan directions^[48]

Table 1. Comparison of structure and performance of Cs₂AgBiBr₆ based lead-free perovskite solar cells