Encapsulation: The path to commercialization of stable perovskite solar cells

Metal halide perovskite solar cells (PSCs) have attracted much attention because of their low-cost fabrication and high efficiency. However, the poor stability of these devices remains a key challenge in their path toward commercialization. To overcome this issue, a robust encapsulation technique by employing suitable materials and structures with high barrier performance against the external environment must be developed to protect PSCs. Here, the degradation mechanism of perovskites as light absorbers is discussed to give a direction for development of encapsulation technology. Because of the unique properties of the metal halide hybrid perovskite, existing encapsulation approaches used in commercial photovoltaics, such as silicon solar cells, must be further improved. Thus, an analysis of the currently available encapsulation materials as barriers from ultraviolet light, moisture, oxygen, etc. without sacrificing device performance during the encapsulation process is presented. In addition, this review provides a comprehensive overview of various encapsulation techniques and configurations, highlighting their strengths and limitations. Finally, suggestions are given for accelerating the development of encapsulation materials and structures to address stability issues and facilitate commercialization of PSCs.