## 4 Conclusions  
In this study, we proposed a novel approach to enhance the photodetection and stability of triple-cation perovskites (Cs\({}_{\gamma}\)FA\({}_{0.9}\)MA\({}_{0.1}\)PbI\({}_{3}\)) through compositional engineering and MAI post-treatment, without the need for the introduction of new materials we fabricated a triple-cation (CsFAMAPbI\({}_{3}\)) perovskite-based UVC PD and compared its electrical properties and stability with those of a conventional double-cation (FAMAPbI\({}_{3}\)) perovskite-based sensor. We systematically evaluated the photoelectric performance and \begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{2}{*}{**Photoactive Material**} & \multicolumn{2}{c}{**Detectable**} & \multirow{2}{*}{**On/Off Ratio**} & \multicolumn{2}{c}{**Detectivity**} & \multirow{2}{*}{**Structure**} & \multirow{2}{*}{**Refs**} \\  & \multicolumn{1}{c}{**Wavelength (nm)**} & & & & \\ \hline Cs\({}_{0.05}\)FA\({}_{0.9}\)MA\({}_{0.1}\)PbI\({}_{3}\) & 254 & 23.94 & 3.52 \(\times\) 10\({}^{14}\) & NIP & this study \\ \hline (FAPbI\({}_{3}\))\({}_{1.3}\)(MAPbBr\({}_{3}\))\({}_{\chi}\) & 254 & 337.14 & 7.57 \(\times\) 10\({}^{10}\) & NIP & [29] \\ \hline (FAPbI\({}_{3}\))\({}_{0.97}\)(MAPbBr\({}_{3}\))\({}_{0.03}\) & 254 & 103 & 4.65 \(\times\) 10\({}^{11}\) & NIP & [30] \\ \hline FAMAPb(I\({}_{x}\)ClyBr\({}_{1-x,y}\)) & 254 & 1.05 \(\times\) 10\({}^{12}\) & 4.71 \(\times\) 10\({}^{12}\) & NIP & [31] \\ \hline (FA)\({}_{x}\)(MA)\({}_{1-x}\)PbI\({}_{3}\) & 254 & - & 4.47 \(\times\) 10\({}^{13}\) & NIP & [32] \\ \hline \end{tabular}
\end{table} 
Table 2: Performance comparison of perovskite PDs. Figure 8: Aging behavior of perovskite PDs under ambient conditions. durability of the PD by optimizing the Cs concentration. The XRD results confirmed that the double-cation perovskite maintained its crystal structure even after the incorporation of Cs. The characteristic diffraction peaks of the \(\alpha\)-phase perovskite were preserved. Notably, at Cs = 0.05, the diffraction peaks exhibited enhanced intensity and a sharper definition, indicating an increase in crystallinity and the formation of a denser lattice. This suggests that Cs incorporation reduces the defect density and enhances the overall structural stability of perovskite thin films. The sensor with the optimum Cs concentration of 0.05 showed the best performance. The photocurrent increased by 7.25%, while the responsivity (R) and detectivity (D*) reached the maximum values of 58.2 mA/W and 3.52 \(\times\) 10\({}^{14}\) Jones, respectively. Furthermore, the CsFAMAPbI3-based sensor exhibited superior long-term stability, showing a 4.6% improvement compared with its double-cation counterpart, thereby demonstrating enhanced durability. The incorporation of Cs contributed to improved structural stability, as confirmed by the analysis of the Goldschmidt tolerance and octahedral factors, which indicated that the Cs-doped structure remained stable. Our fabricated triple-cation (CsFAMAPbI3) perovskite-based UVC PD outperformed conventional double-cation perovskite structures in terms of photoelectric performance and long-term stability. These findings suggest that the developed sensor holds significant potential for application in high-performance, long-term stable UVC PDs and other optoelectronic devices in which stability and efficiency are critical. Recent developments in flexible, self-powered UV detectors employ different materials and device architectures, making direct comparison challenging [33]. Therefore, future work may explore the integration of this system into flexible or self-powered devices. Investigation, J.S.K. ; supervision, H.W.C. and S.K. ; validation, H.W.C. and S.K. ; writing--original draft, J.S.K. ; writing--review and editing, H.W.C. and S.K. All authors have read and agreed to the published version of the manuscript. This study was supported by the Gachon University Research Fund 2023 (GCU-202400630001). Not applicable.