path of perovskite solar cells (PSCs). [2] A major reason for perovskite instability is the presence of organic cation CH 3 NH 3 + (MA + ) and HC(NH 2 ) 2 (FA + ) which are hygroscopic and volatile. [3] An effective approach to fight the thermal instability is the replacement of an organic cation with an inorganic cation. Within the perovskite composition space, cesium (Cs + ) is the only inorganic cation that can successfully crystallize in the cubic perovskite phase. [4,5] Cahen with co-workers 2015 established that all-inorganic perovskites have the potential to work equally well as hybrid perovskites and can provide better stability. [6,7] An extensive work was hereafter done by researchers on CsPbX 3 leading to its emergence as a rising star of photovoltaics. Interestingly, CsPbX 3 perovskite exists in different phases depending on temperature, synthesizing conditions, and composition. [8,9] Among the different halogen counterparts of CsPbX 3 , the iodine counterpart exhibits the most suitable optical bandgap (1.7 eV) for solar cells per Shockley-Queisser (SQ) limit. Owing to the rigorous work including doping, alloying, and interface engineering, CsPbX 3 showed an outstanding enhancement in power conversion efficiency (PCE) from 5.72% in 2015 to 20.7% in 2021. [6,10] Also, the other halogen counterparts are studied for low-temperature crystallization and stabilization. Apart from single-junction solar cells, research in the next generation of PSCs is also focusing on the formation of tandem solar cells (TSCs). TSCs are utilizing wide-bandgap semiconductors as front cells and narrow-bandgap semiconductors as rear cells to absorb high and low-energy photons, respectively. The bandgap of CsPbX 3 is quite suitable to serve as the front cell in TSCs with another low-bandgap perovskite, silicon, organic semiconductor blends, and CIGS as the rear cell. [11] Cao et al. proposed using inorganic perovskites in conjunction with organic semiconductors. [12] Recently, Wang et al. successfully utilized a wide-bandgap CsP-bI 2 Br semiconductor and an organic blend of narrow-bandgap PM6:Y6-BO to fabricate perovskite/organic tandem solar cells which yielded an efficiency of 21.1%. [13] Although thermally stable, CsPbI 3 faces the problem of moisture instability and high-temperature crystallization. This instability is attributed to the small ionic radii of Cs (167 pm) which result in a Goldschmidt tolerance value of 0.81. [14] The all-inorganic CsPbX 3 (X-Cl, Br, I) perovskite has the potential to solve the practical issues of environmental instability due to the presence of hygroscopic organic cations in the hybrid organic-inorganic perovskites. The promising CsPbX 3 perovskite exists in different crystallographic phases depending upon the composition and processing conditions which potentially impact the film morphology, device efficiency, and stability. Stabilizing the black metastable phase at room temperature has substantially solved the problem of high crystallization temperature, which is the main roadblock in managi...