Photostability and Moisture Stability of CH₃ NH₃ PbI₃ -based Solar Cells by Ethyl Cellulose

Organic-inorganic hybrid perovskite solar cells have achieved high power conversion efficiencies (PCE) of around 22 %, comparable to conventional silicon and thin-film solar cells. However, the poor stability of the perovskite material is one of the significant drawbacks for its practical application. In moderate humidity, the perovskite hydrates and decomposes within hours or a few days, which deteriorates the device efficiency rapidly. Herein, is demonstrated the moisture stability and photostability of CH₃ NH₃ PbI₃ can be greatly improved through the interaction between ethyl cellulose (EC) and perovskite crystals. It is found that the CH₃ NH₃ PbI₃ film with EC incorporation is stable over 5 days in 60 % relative humidity (RH) under ambient indoor light, whereas the conventional CH₃ NH₃ PbI₃ film without EC is degraded in 1 day. After being stored in 60 % RH under ambient indoor light for 2.5 days, the solar cell with EC incorporation shows a PCE decrement from 14.08 % to 8.21 %, whereas that without EC is nearly entirely degraded (PCE=0 %). Nuclear magnetic resonance (NMR) spectroscopy shows that hydrogen bonding between EC and CH₃ NH₃ PbI₃ accounts for the improved moisture stability by stabilizing the crystal structure.