Inorganic Encapsulation Method Using Solution-Processible Polysilazane for Flexible Solar Cells

In this work, we employed the method of perhydropolysilazane (PHPS) conversion into silica for encapsulating flexible perovskite solar cells (PSCs). The conversion process was conducted by the vacuum ultraviolet (VUV) irradiation method. To avoid the degradation of PSCs by the PHPS solution and high-energy light illumination of VUV (λ = 172 nm), the CdSe/ZnS-quantum dot (QD) was diffused in the polydimethylsiloxane matrix as a barrier layer. The barrier layer efficiently blocked the penetration of the PHPS solution into PSCs and UV illumination during the PHPS curing process. The resulting encapsulation layer presented a water vapor transmission rate of 8.63 × 10^–3 g m⁻² d^–1 (37.8 °C/100 RH %, relative humidity), enhancing the performance of PSCs because of the luminescence downshifting from QDs. Finally, we applied this encapsulation method to flexible PSCs. Their lifetime was enhanced by more than 400 h under ambient temperature.