Suppressing degradation via natural antioxidant encapsulation toward highly efficient and stable perovskite solar cells

Oxidation of hybrid perovskite composed of organic-inorganic materials has caused significant problems in performance and stability of perovskite solar cells (PSCs), because the hybrid perovskite oxidation induces considerable decrease in crystallinity and quality of hybrid perovskites. In this research, we report an improved crystallization of hybrid perovskite films achieved through addition of a potent antioxidant derived from garlic, known as allicin. Defect sites within the hybrid perovskite film, which arise during annealing and ageing processes, are effectively managed by the antioxidant properties of allicin, particularly at elevated temperatures. Acting as an in situ encapsulator for the hybrid perovskite, the antioxidant efficiently regulates defect sites by supplying protons and neutralizing free radicals. This leads to enhanced power conversion efficiency (PCE) and long-term stability of PSCs. Consequently, addition of the antioxidants to the hybrid perovskite film facilitates charge-trap passivation and charge extraction, resulting in an increase in PCE from 22.89 to 24.50 %. Moreover, the encapsulated PSC by the antioxidants retains approximately 92 % of its initial PCE even after exposure to ambient conditions for over 190 days. It is remarkable results from the perspective of the efficiency and the stability. This study provides effective and eco-friendly guidelines for suppressing the oxidation of hybrid perovskite, achieving both high efficiency and stability in PSCs.