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Metal halide perovskites have recently garnered significant attention as a fundamental emitter due to their high carrier mobility, strong light absorption, high monochromaticity, and tunable emission bandgap. However, the brightness, efficiency, and stability issues have limited their potential applications in blue region. To break through these limitations, researchers have investigated different dimensions of perovskites to seek an excellent emitter. To date, the quantum confinement and coordination octahedron monomer arrangement perovskites still lack of systematic cognition. In this review, the molecular and morphological dimensions of blue perovskite emitters are summarized. The differences and relationships between these dimensions in terms of their fabrication and properties are also explored. Furthermore, recent advances in blue light enhancement strategies to address the challenges in various morphological and molecular structures are highlighted. Finally, the main challenges and future directions are discussed for the development of perovskite blue LEDs. [ABSTRACT FROM AUTHOR]

The elimination of methylammonium (MA) cation from mixed tin–lead (Sn–Pb) narrow‐bandgap (NBG) perovskites is an effective approach to enhance the operational stability of all‐perovskite tandem solar cells (TSCs). Unfortunately, the uncontrolled nucleation and crystallization processes of MA‐free Sn–Pb perovskites usually lead to inferior film quality and device performance. Herein, a bimolecular crystallization modulation strategy is reported by using guanidine thiocyanate (GuaSCN) and aminoacetamide hydrochloride (AHC) together as additives to improve the film quality of MA‐free Sn–Pb perovskites. It is demonstrated that the use of bimolecular additives can effectively improve the crystallinity, increase the grain size, and induce a preferred (100) orientation for the corresponding films, leading to high‐quality absorber with considerably reduced defect density and suppressed non‐radiative recombination. In addition, the bimolecular additives can reduce the self‐p‐doping hole concentration within the perovskite films and enhance the charge extraction at the perovskite/electron transport layer interface. The modified NBG perovskite solar cells deliver a power conversion efficiency (PCE) of 22.14%. Coupled with the wide‐bandgap (WBG) subcell, the all‐perovskite TSCs give a champion certified PCE of 27.15%, which is the highest certified PCE for MA‐free all‐perovskite TSCs. Encapsulated tandem devices maintain 90% of the initial PCE after 473 h operation. [ABSTRACT FROM AUTHOR]