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.

A method for enhancing the moisture barrier property of polydimethylsiloxane (PDMS) polymer films is proposed. This is achieved by filling the PDMS free volume with aluminum oxide (AlOx).

In this study, we developed the universal encapsulation method using poly(vinyl alcohol- co -ethylene) (EVOH) to improve the water stability of perovskite solar cells. In order to enhance the moisture barrier property, we utilized SiO 2 and graphene oxide (GO) fillers in the EVOH matrix. First, UV-treated SiO 2 increased the dispersibility in the EVOH matrix and made the penetrating path more complicated, which led to a better moisture barrier property. The water vapor transmission ratio (WVTR) is enhanced from 4.72 × 10 –2 (EVOH only) to 1.55 × 10 –2 (EVOH with SiO 2 filler) g/m 2 day. Second, we found that GO reduce the unreacted hydroxyl groups that could attract water molecules at the surface of EVOH. The addition of GO increased the WVTR up to 3.34 × 10 –3 g/m 2 day. Finally, our EVOH-based film successfully encapsulated without the efficiency drop. The encapsulated devices surprisingly maintained 86% of their performance even under direct contact with water for 5 h.

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