## 2 Results
In particular, the intensity emission in WA is 2.8 times higher than the one in V, thus about nine times higher than the one of Sample #F. The peak position of the BE and FE emission bands is red-shifted in WA by about 7.0 and 5.4 meV, respectively, and a FWHM reduction is observed. In addition, also in this sample, the observed variations are fully reversible if the vacuum is restored in the sample chamber. To get a deeper insight in the origin of the PL intensity dependence on the different environmental conditions, we performed time resolved spectroscopy by recording TR-PL in experimental conditions similar to those used for CW-PL in Figure 3.  
The TR-PL signal of Sample #F in vacuum shows (see Figure 4a) a non-exponential relaxation, which can be reproduced by the superposition of three exponential decays:  
\[I\left(t\right)=y_{0}+A_{1}e^{-t/\tau_{1}}+A_{2}e^{-t/\tau_{2}}+A_{3}e^{-t/\tau _{3}} \tag{1}\]  
The multi-exponential decay analysis evidences (see Figure 3a) two fast recombination processes with time constants \(\tau_{1}\approx 1.9\) ns and \(\tau_{2}\approx 11.5\) ns, and a slower process with time constant \(\tau_{3}\approx 70\) ns. To ascribe these decay processes, we initially observe that the TR-PL have been recorded at the PL spectrum maximum; thus, considering that the FE band lies within the spectral broadening of BE one, the TR-PL signals contains the superposition of the BE and FE relaxation dynamics. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Sample** & \begin{tabular}{c} **E\({}_{1}\)** \\ **(eV)** \\ \end{tabular} & \begin{tabular}{c} **FWHM\({}_{1}\)** \\ **(meV)** \\ \end{tabular} & \begin{tabular}{c} **A\({}_{1}\)** \\ **(eV)** \\ \end{tabular} & \begin{tabular}{c} **E\({}_{2}\)** \\ **(meV)** \\ \end{tabular} & \
\begin{tabular}{c} **FWHM\({}_{2}\)** \\ **(meV)** \\ \end{tabular} &
\begin{tabular}{c} **A\({}_{2}\)** \\ **(meV)** \\ \end{tabular} \\ \hline \#F V & 2.3873 \(\pm\) 0.0009 & 149 \(\pm\) 2 & 0.913 \(\pm\) 0.018 & 2.405 \(\pm\) 0.002 & 50 \(\pm\) 6 & 0.087 \(\pm\) 0.017 \\ \#F WA & 2.3705 \(\pm\) 0.0005 & 134.4 \(\pm\) 0.9 & 1.209 \(\pm\) 0.010 & 2.3939 \(\pm\) 0.0009 & 43 \(\pm\) 3 & 0.91 \(\pm\) 0.09 \\ \#A V & 2.3720 \(\pm\) 0.0003 & 125.1 \(\pm\) 0.5 & 0.903 \(\pm\) 0.005 & 2.3955 \(\pm\) 0.0004 & 44.5 \(\pm\) 1.3 & 0.097 \(\pm\) 0.004 \\ \#A WA & 2.3650 \(\pm\) 0.0004 & 116.1 \(\pm\) 0.6 & 2.64 \(\pm\) 0.02 & 2.3901 \(\pm\) 0.0008 & 40 \(\pm\) 3 & 0.163 \(\pm\) 0.016 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Best fit values of the peak energy (E), the FWHM, and the integrated intensity (A) of the two best fit Gaussians. The amplitude values are normalized to the integrated PL intensity in V, in order to better evidence their relative variation in WA. Figure 3: Integrated intensity during time under continuous laser irradiation in vacuum and wet air evidencing the clear intensity increase in wet air with respect to the value in vacuum: Sample #F (**a**); and Sample #A (**b**). Moreover, the presence of different decay times between a few and hundreds of nanoseconds has already been observed in CsPbBr\({}_{3}\) NCs [32], and allows tentatively ascribing \(\tau_{1}\) to FE trapping, \(\tau_{2}\) to FE recombination, and \(\tau_{3}\) to BE relaxation. The relative amplitudes of these processes are 68.4%, 27.4%, and 4.2%, respectively. When the atmosphere changes from V to WA, the following effects are observed for Sample #F (see Figures 4a and 5a):  
1. The peak intensity slightly increases (about 13%) (see inset of Figure 4a). 2. The two faster decay times remain essentially unchanged (\(\tau_{1}\approx 1.9\) ns and \(\tau_{2}\approx 11.5\) ns), while a clear increase of the longest decay time \(\tau_{3}\) from about 70 ns to about 100 ns is observed. 3. The pre-exponential amplitude of the fastest process A\({}_{1}\) slightly decreases (about 4%), while the amplitudes A\({}_{2}\) and A\({}_{3}\) increase of about 40% and 36%, respectively.