Perovskite solar cells attract widespread attention due to their impressive power conversion efficiencies, high absorption coefficients, tunable bandgap, and straightforward manufacturing protocols. However, in the process of further development and optimization toward mass production, the long‐term stability stands as one of the most urgent challenges that need to be overcome. Given the excellent thermal stability and high structural designability, ionic liquids (ILs) are relatively green room‐temperature molten salts that have been widely applied to perovskite photovoltaic devices with promising results in view of improved stability and enhanced device performance. In this review, the reasons and mechanisms of instability of such devices under external and internal factors are analyzed. The current strategies of ILs engineering for improved stability of the devices are classified and summarized, including the IL‐assisted perovskite film evolution and IL‐modified photophysical properties of the perovskite photoactive layer and the related stability and photovoltaic performance of the devices. The challenges that stand as obstacles toward further development of perovskite solar cells based on IL engineering and their prospects are also discussed.

Over the past decade, perovskite photovoltaics have approached other currently available technologies and proven to be the most prospective type of solar cells. Although the many-sided research in this very active field has generated consistent results with regards to their undisputed consistently increasing power conversion efficiency, it also produced several rather contradictory opinions. Among other important details, debate surrounding their proneness to surface degradation and poor mechanical robustness, as well as the environmental footprint of this materials class remains a moot point. The application of ionic liquids appears as one of the potential remedies to some of these challenges due to their high conductivity, the opportunities for chemical 'tuning' of the structure, and relatively lower environmental footprint. This article provides an overview, classification, and applications of ionic liquids in perovskite solar cells. We summarize the use and role of ionic liquids as versatile additives, solvents, and modifiers in perovskite precursor solution, charge transport layer, as well as for interfacial and stability engineering. Finally, challenges and the future prospects for the design and/or selection of ionic liquids with a specific profile that meets the requirements for next generation highly efficient and stable perovskite solar cells are proposed.

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Metal halide perovskites can be readily synthesized, they exhibit tunable physical properties and excellent performance, and they are heavily studied optoelectronic materials. Compared to the typical three-dimensional perovskites, morphological-level one-dimensional (1D) nanostructures enable charge transport and photon propagation with low exciton binding energies and long charge-carrier diffusion lengths, while molecular-level 1D nanostructures exhibit good compositional and structural flexibilities, highly tunable bandgaps, strong quantum confinement effects, and excellent ambient stabilities. The 1D natures of these emerging halide perovskites enhance the performance of optoelectronic devices. Herein, we highlight recent progress realized in the syntheses and characterizations of both morphological- and molecular-level 1D halide perovskites with tunable structures, compositions, and properties, as well as their photovoltaic, light-emission, and photodetection applications. In addition, current challenges, future prospects, and promising research directions are discussed to provide guidance in advancing the field of 1D perovskites.