Fig. 2

Photoluminescence spectra of MAPbI₃ MWs at different stages of humidity exposure. a As-prepared sample, after the b 1st week at 45% RH, c 4th week at 55% RH, and d 5th, e 7th, f 9th, and g 11th weeks at 80% RH. All spectra taken in ambient conditions, with an excitation wavelength of 633 nm, a laser power ~ 5 μW, an acquisition time of 10 s, and a laser spot diameter of ~ 1 μm on the sample