Advanced Interface Engineering for Perovskite Solar Cells: The Way to Ensure Efficiency and Stability

초록

Photovoltaics (PVs) are currently the most economical and location-independent source of electricity generation, and their demand is growing rapidly as a sustainable renewable energy source. PVs are playing an increasingly vital role in global efforts to protect the environment and reduce carbon emissions, while also expanding into previously unexplored areas such as building integrated PV (BIPV), space PV, and indoor PV, thereby increasing the demand for various technical requirements. To meet these growing demands requirements simultaneously, the development of new PV materials is essential-materials that offer improved cost-effectiveness, flexible form factors, and access to new market applications. Organic-inorganic halide perovskites (PVSKs) are well suited to meet these requirements due to their excellent light absorption, long charge carrier lifetimes, low-cost processing, and inexpensive raw materials. Since first reported by Miyasaka's group in 2009 and subsequently demonstrated as an all-solid-state solar cell by Park's group in 2012, they have become one of the most intensively studied materials in the solar cell field. Through the efforts of many researchers, perovskite solar cells (PSCs) have achieved a certified power conversion efficiency of over 26%, the highest among all thin-film solar cells, based on optimized planar heterojunction architectures. This achievement has become a source of technological inspiration and has accelerated research aimed at commercialization beyond the fundamental level. However, key technical challenges-such as long-term stability under external conditions, scalability, module integration, and tandemization with other PV technologies-cannot be resolved by improvements in the PVSK absorber alone. Interfaces between the functional layers in the heterojunction, where photogenerated charges are transferred, have been identified as critical sites of charge loss. As such, interface engineering has emerged as a crucial research area. In particular, recent studies have reported innovative strategies such as structural interface design and multifunctional interface engineering-approaches that go beyond traditional methods-highlighting the need to focus on these emerging trends. In this Account, we present a new classification scheme for interface engineering that introduces novel categories such as surface structural engineering. We also review recent advances in state-of-the-art interfacial strategies across four key domains: (i) structural engineering, (ii) surface treatment, (iii) electron transport layers, and (iv) hole transport layers, with an emphasis on our own research contributions. We further identify the main challenges and research directions within each area and highlight how our group, along with others, has addressed these issues-such as optimizing perovskite surface design or identifying key criteria for selecting surface treatment materials and charge transport layers. Finally, we summarize the progress to date and offer perspectives on future challenges to overcome theoretical efficiency limits and realize the commercialization of PVSK photovoltaics.

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