Nano-engineering halide perovskites: towards energy harvesting, nano-plasmonic sensing and photoflexoelectric applications

Halide perovskites can be classified as (1) organic inorganic hybrid and (2) inorganic halide perovskites. Monolithic perovskite/silicon tandem solar cells, which are based on these materials, have already demonstrated extraordinarily high performances in the field of photovoltaics, with a current efficiency of 34.6%, breaking the efficiency limit of silicon solar cells, while single-junction perovskite solar cells have achieved an efficiency of 27%. Currently, halide perovskites are successfully employed not only in photovoltaics but also in many other related potential optoelectronic applications. Therefore, the origin of their multifunctional properties, remarkable energy harvesting and emitting efficiency and the corresponding potential applications in various optoelectronic devices have become controversial issues and hot topics of academic research. In this review, the nano-engineering strategies, microscopic origins and mechanisms of halide perovskites are reviewed in detail to clarify the origin of their multifunctional properties, such as tunability, ferroelasticity, piezoelectricity, pyroelectricity and thermoelectric properties. Moreover, the coexistence of multiple properties in halide perovskites enables synergistic applications and multifunctional perspectives, such as emerging energy harvesting, conversion technologies, nano-plasmonic sensing and electromechanical applications, which are now open for the scientific community for further detailed investigations. To successfully explore this field, advanced nanometer-scale domain characterization tools are highly relevant to understand the microscopic origin of these electrical properties, which will benefit commercial enterprises and research institutions. The primary aim of this review is not only to highlight the microscopic origin but also identify the factors and issues affecting the successful understanding and presence or absence of these electrical parameters. Finally, the significant challenges in the operation of halide perovskites owing to temperature-, moisture-, light-, and air-induced material degradation and device deteriorations as well as lattice instability, nanoscale defects, surface and bulk defects are proposed to be considered for future research on this topic.