Stability study of emerging PV materials – organic-inorganic hybrid perovskites

Dr. Yong Zhang
Research Highlight

Organic-inorganic halide perovskites (e.g., MAPbX3, MA= CH3NH3) emerged only a few years ago as promising candidate materials for low-cost efficient solar cells and various other optoelectronic applications. In the past, it typically took several decades of research efforts for other materials to reach a performance target ready for commercialization. In contrast, within 6 years, the efficiency of low-cost solution processed perovskite solar cells has reached 22%, a milestone only a few materials has reached. However, a formidable challenge is the poor stability of these devices due to both intrinsic and extrinsic mechanisms that are not yet adequately understood. Prof. Yong Zhang’s group, in collaboration with scientists in Korea, China, and NREL, has reported (in Phys. Rev. X) a multiple stage structure transformation in an effort attempting to understand both ground and photo-excited states stability of this material. He is a co-PI on a new UNC Research Opportunities Initiative project “Hybrid Perovskite Materials and Technologies” in which his group and collaborators at UNC-CH, NCSU, and NCCU will continue the effort to understand the intrinsic and extrinsic mechanisms of the instability, and develop mitigation methods. As shown below, his group has shown how increasing laser power or temperature makes the Raman spectrum of the perovskite evolving from a practically featureless to one showing multiple well resolved peaks of PbI2. His group is also interested in other types of hybrid materials, such as II-VI based hybrid nanostructures that have been shown to exhibit many unusual physical properties, such as room temperature free exciton emission and zero thermal expansion. These two families of organic-inorganic hybrid materials are complementary in sciences and applications.