## 5 Conclusions  
The performance of a new encapsulation method to protect perovskite solar cells from external agents such as moisture, oxygen, heat and UV light has been tested by monitoring the degradation of the perovskite layer due to full solar irradiation and UV light under normal humidity conditions. In these conditions, the MAPbI\({}_{3}\) perovskite samples that were not encapsulated showed visual and optical degradation after they were subjected to UV irradiation. Thus, optical ellipsometry analysis of non-encapsulated MAPbI\({}_{3}\) samples showed a decrease in the absorbance of the samples from 400 nm to 700 nm, whereas the band gap increased from 1.6 eV to 2.2 eV, requiring more energy to generate the electron hole pair. Moreover, the FTIR analyses showed an intensity reduction in the functional groups of ammonium, defined by the vibration modes located at 3181 cm\({}^{-1}\) (N-H stretch), 3124 cm\({}^{-1}\) (N-H stretch) and 1465 cm\({}^{-1}\) (symmetric NH\({}_{3}\)\({}^{+}\) bend), which can be used as indicator peaks marking the degradation of perovskite caused by the UV light. However, the encapsulated samples endured UV irradiation, keeping the absorbance curves (by using a spectrometer) and the intensity of the characteristic peaks of the ammonium functional groups (by using FTIR techniques) constant after 350 h of continuous irradiation. Furthermore, the intermediate complex found at 1660 cm\({}^{-1}\), which is sensitive to hydration [75], was not observed in any of the samples. All these results indicate that the new encapsulation method used in this study, protects the perovskite layer from degradation due to UV irradiation at ambient conditions. Figure 12: IV curve of non-encapsulated pristine sample (black line), encapsulated pristine sample (orange line) and encapsulated sample, after 350 h exposed to full solar irradiation (red line). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**ID** & **V\({}_{\text{oc}}\) (V)** & **J\({}_{\text{sc}}\) (mA/cm\({}^{2}\))** & **FF (\%)** & **PCE (\%)** \\ \hline MAPbI\({}_{3}\) & 1.09 & 21.66 & 68.3 & 16.18 \\ MAPbI\({}_{3}\) + EVA & 1.09 & 20.61 & 68.0 & 15.31 \\ MAPbI\({}_{3}\) + EVA & 1.09 & 20.58 & 67.8 & 15.23 \\ (full irradiation 6051 kW/m\({}^{2}\)) & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Simulation results: non-encapsulated pristine sample, encapsulate pristine sample and encapsulate sample, after 350 h exposed to full solar irradiation. Additionally, the results obtained from optical ellipsometry and FTIR measurements indicate that the addition of an ETL layer does not affect the device light absorption characteristics and keeps the band gap stable. Interesting enough, the results also indicate that the addition of an ETL layer to the non-encapsulated samples delays the degradation process due to a decreased UV absorption by the perovskite and EVA layers, since the ETL layer acts as a shield, absorbing part of the incident UV irradiation. However, studies regarding longer periods of exposure are still necessary in order to fully characterize this phenomenon. Finally, the parameters measured on the pristine samples and the ones that were subjected to UV irradiation at ambient conditions, together with other parameters obtained in the literature, allowed us to run SCAPS-1D simulations in order to estimate the performance of their corresponding PSCs. The results obtained also confirm that encapsulated devices remained stable under different solar conditions, while the non-encapsulated ones showed a remarkable reduction in their short circuit current due to UV irradiation. Conceptualization, L.O., C.M., S.G.-P. and B.G.-D.; methodology, L.O., C.M., S.G.-P. and B.G.-D.; software, L.O. ; validation, L.O., C.M., S.G.-P. and B.G.-D.; formal analysis, L.O., C.M., S.G.-P. and B.G.-D.; investigation, L.O. and C.M. ; resources, L.O., C.M., S.G.-P. and B.G.-D.; data curation, L.O. ; writing--original draft preparation, L.O.