29Abstract Lead-halide compounds of perovskite structure have emerged as a new class of photovoltaic materials, achieving high power conversion efficiencies (PCE) of over 26% in an unprecedented short period. Despite the startling device efficiency, an unavoidable PCE down over time is a major hurdle for real-world operation. Many studies have shown that the degradation of the device is triggered by many external and internal factors. Especially, the accelerated PCE loss caused by simultaneous thermal and light stress is critical. Developing effective countermeasures based on the analysis of this loss mechanism is essential.We addressed these challenges through chemical and electronic investigations. The buried interface analysis between the perovskite layer and interfacing materials using Hard X-ray photoelectron spectroscopy (HAXPES) and transmission electron microscopy (TEM) revealed that the chemical decomposition of the MAPbI3 perovskite is interface dependent.1 In fact, the development of new interface materials conducted in parallel to the mechanism investigations, we realized that sputter-deposited NiOx (sp-NiOx) layers were effective to slow down the device degradation.2 Being robust inorganic interface material and processible at room temperatures, the sp-NiOx could be an ideal material for the practical applications. Another issue is the mobile ions in lead-halide perovskites, which are mixed conductors. The ionic charge accumulate at the perovskite near the interfacing materials, affect the change injection/extraction efficiencies, and thus short-term as well as long-term device performances. Analysis on the dynamic ion species through an operand HAXPES study and interface material design highlight an intrinsic factor essential for enhance the long-term stability of perovskite solar cells.3 Similarly, we will discuss that further investigations on the interface materials and the treatments of the perovskite surfaces resulted in the improvement of the device performance.4References:1. Gueye, I. et.al. ACS Appl. Mater. Interfaces 2021, 13 (42), 50481-50490.2. Islam, M.B. et.al. ACS Omega 2017, 2, 2291; Sol. Energy Mater. Sol. Cells 2019, 195, 323.3. Gueye, I. et.al. Chemistry of Materials 2023, 35 (5), 1948.4. Khadka, D.B. et.al. Nat. Commun. 2024, 15 (1), 882.Yasuhiro ShiraiDevelopment of Interface Materials for Perovskite Solar CellsDr. Yasuhiro Shirai completed his PhD at Rice University, Houston, TX. He has investigated nanomaterials for electronic devices and machines, especially focused on the design and synthesis of new organic materials. His aim at NIMS is to develop the next generation photovoltaic materials and devices.Photovoltaic Materials Group, Research Center for Energy and Environmental Materials (GREEN), National Institute for Materials Science (NIMS)NIMS Talk 1
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