Fig. 2. Pristine and SnI₄-rich samples: (a) absorption spectrum and PL emission (excitation with 450 nm CW laser at 100 mW cm⁻²), (b) lifetimes extracted from single exponential fitting of the TRPL decays as function of excitation density. The fluence dependence for the SnI₄-rich sample is measured with Transient absorbption (TA) spectroscopy, (c) external PLQY taken with increasing excitation density, experimental points indicated by a star, at excitation densities lower than 10¹⁷ cm⁻³ were measured with CW excitation. Experimental points indicated by dots, were measured with pulsed excitation (repetition rate 500 kHz) to avoid sample degradation. The relative value is normalized on the absolute PLQY at 1 sun (about 5 × 10¹⁴ cm⁻³) measured with an integrating sphere. Non normalized data points are reported in Fig. S16b (ESI†).