A Novel Approach for the Development of Moisture Encapsulation Poly(vinyl alcohol-co-ethylene) for Perovskite Solar Cells

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.