New Nature Materials from Jun He, Yongbo Yuan of Central South University, and Jinsong Huang of UNC: Mobile Iodide Trapping for Highly Light-Stable and Reverse-Bias-Stable Perovskite Solar Cells

On April 29, 2024, Jun He, Yongbo Yuan of Central South University, and Jin-Song Huang of the University of North Carolina published in Nature Materials a study on the use of mobile iodide trapping to achieve highly light-stable and reverse-bias-stable perovskite solar cells. For halide perovskites, which are prone to photodegradation and ion migration, iodide-related defects—such as molecular iodine (I₂) and iodine vacancies—are unavoidable. Even at low concentrations, these defects can trigger self-accelerating chemical reactions, posing a severe challenge to the durability of perovskite solar cells. Fortunately, before I₂ can degrade the perovskite under illumination, it typically diffuses over long distances. Consequently, harmful I₂ can be captured by interfacial materials with strong affinity for iodide/polyiodide (Ix⁻) species, such as fullerene and perfluorodecyl iodide. However, fullerene in direct contact with the perovskite layer fails to confine Ix⁻ ions within the perovskite active layer and instead gives rise to detrimental iodine vacancies. In contrast, perfluorodecyl iodide exhibits directional Ix⁻ affinity through halogen bonding, enabling effective capture and confinement of Ix⁻. As a result, a planar-perovskite solar cell has been developed that demonstrates more than tenfold improvement in UV irradiation and thermal–light stability (under 85°C and one-sun illumination) and over a thousandfold enhancement in reverse-bias stability (as assessed by the ISOS-V aging test).