Phase-Purity Engineering in Quasi-2D Perovskites for Amplified Spontaneous Emission

• • Achieved 99.85% phase purity for n=8 quasi-2D perovskite via solvent-sieving, eliminating low-n impurity phases that cause interfacial defects and non-radiative recombination, directly improving charge injection efficiency for lasing applications. • • Crystallinity enhancement evidenced by (001) peak FWHM reduction from 0.22 to 0.16 nm and intensity increase from 3,304 to 16,129, indicating larger grains and reduced lattice disorder, which is critical for minimizing scattering losses in thin-film lasers. • • Carrier lifetime extended from 5.38 to 6.98 ns, attributed to suppressed trap-assisted recombination, leading to higher photoluminescence quantum yield and lower non-radiative losses, essential for achieving population inversion at lower pump fluences. • • Amplified spontaneous emission threshold lowered to 13.82 μJ cm−2, a 12.5% reduction compared to pristine films (15.8 μJ cm−2) and 35% lower than other conventional techniques, demonstrating a viable path to low-threshold perovskite lasers for commercial photonic devices.