Comparative Analysis of the Commonly used Electron Transporting Layers in High Efficiency Perovskite Solar Cells

Since the last twelve years, efficiency of perovskite-integrated photovoltaic devices has significantly advanced as of an initial 3.8% to an impressive 27% till date. In contrast, traditional solar cells, particularly those based on silicon, have exhibited only a marginal improvement of 1.1% over the same period. This remarkable progress, fueled by the native optoelectronic behaviour of perovskites and continuous optimization of both the perovskite/active layer and electron transport layers (ETLs), have evolved as a core concept in photovoltaic research. This review brings forth an in-depth picture of various electron transport materials (ETMs) employed in perovskite-based solar cells (PSCs). It begins with the outline of architecture, framework and configuration of perovskite-based solar cells, accompanied by a thorough discussion of the role and significance of electron transport layers in enhancing device performance. The classification of electron transport materials into organic and inorganic categories is explored, with their respective merits and limitations highlighted. Particular emphasis is given to representative materials such as C60 and PCBM (organic), and ZnO, TiO2, WS2, SnO2, and CeO2 (inorganic). Furthermore, the review discusses recent advancements in the design and application of novel ETLs aiming for further optimization of performance and longevity of PSC devices.