Progress on the stability and encapsulation techniques of perovskite solar cells

Perovskite solar cells (PSCs) have developed rapidly in the past decade and its certified power conversion efficiency (PCE) has skyrocketed to 25.7%. Though high PCE has been obtained, the relatively poor long-term device stability still significantly retards the industrial commercialization of this photovoltaic technology. On this account, it is imperative to address the problems of stability issues and achieve high efficiency and high durability simultaneously. In this review, firstly we demonstrate some instability issues and related degradation mechanisms for PSCs, corresponding solutions are summarized as well. Despite the intrinsic instability, encapsulation technique is supposed to be an effective method to improve the long-term stability of PSCs under ambient conditions. Thus, detailed requirements for encapsulation process and encapsulant materials are offered to meet with the environment-sensitive PSCs, especially to temperature, oxygen, moisture and UV light. And a standard protocol for stability tests of perovskite devices is urgently needed to verify the effectiveness of encapsulation and then further accurately select encapsulant materials through comparisons. Herein, we specially presented three currently available encapsulation strategies for perovskite devices, mainly focusing on encapsulation configurations and materials for each type and their roles in preventing the penetration of water vapor and oxygen. In addition, a thorough discussion on the strengths and limitations of different strategies is covered, which helps in the choice of technical route for encapsulation. Finally, a cost-efficient and effective encapsulation method companying with environment-friendly materials is expected to achieve the commercialization of PSCs.