Lu, Shao-AnShao-AnLuGupta, Karan KumarKaran KumarGuptaCHUNG-HSIN LU2025-10-162025-10-162026-01-1501694332https://www.scopus.com/record/display.uri?eid=2-s2.0-105015071631&origin=resultslisthttps://scholars.lib.ntu.edu.tw/handle/123456789/732677Ensuring strong phase stability in red perovskite nanoparticles (R-NPs) is crucial for maintaining the exceptional optoelectronic performances; nevertheless, instability continues to be a significant obstacle to the practical applications. This work utilized a controlled anti-solvent-aided precipitation method to modify the particle sizes of Cs₁₋ₓFAₓPbBr₁.₂I₁.₈ R-NPs and comprehensively examine the impact of particle dimensions on structural phase transitions under ambient circumstances. By accurately adjusting the butyl acetate concentration in the anti-solvent, the dimensions of R-NPs were regulated from 10 nm to 50 nm, therefore successfully inhibiting the transition from the luminous cubic phase to the non-emissive orthorhombic phase. According to structural studies using X-ray diffraction and temperature-dependent photoluminescence measurements, larger R-NPs maintained a stable cubic lattice with less electron–phonon coupling, which resulted in longer photoluminescence retention. Interestingly, films made from 50 nm R-NPs outperformed their smaller counterparts by retaining 40 % of the original emission intensity after 240 h in ambient air. Additionally, the coverage ratio of the color gamut increased in light-emitting diodes made with large R-NPs (98 % of Rec. 2020). According to current findings, the optical properties of Cs₁₋ₓFAₓPbBr₁.₂I₁.₈ R-NPs were improved, and phase transition was efficiently suppressed by increasing the particle dimension. The current findings offer important insights for incorporating R-NPs with future encapsulation or passivation schemes to improve resistance against moisture, oxygen, and photo-induced degradation, paving the way toward more dependable display and optoelectronic applications, even though the main focus of this work is intrinsic phase stabilization via particle size engineering.falseRed-nanoparticlesRoom-temperature synthesisSize-controllableStabilityjournal article10.1016/j.apsusc.2025.1644572-s2.0-105015071631