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Highlights: A comprehensive summary of the representative promising applications of metal halide perovskite materials, including traditional optoelectronic devices (solar cells, light-emitting diodes, photodetectors, lasers), and cutting-edge technologies in terms of neuromorphic devices (artificial synapses and memristors) and pressure-induced emission. For each application, the fundamentals of the field, the current progress and the remaining challenges are provided, based on the up-to-date works. Nowadays, the soar of photovoltaic performance of perovskite solar cells has set off a fever in the study of metal halide perovskite materials. The excellent optoelectronic properties and defect tolerance feature allow metal halide perovskite to be employed in a wide variety of applications. This article provides a holistic review over the current progress and future prospects of metal halide perovskite materials in representative promising applications, including traditional optoelectronic devices (solar cells, light-emitting diodes, photodetectors, lasers), and cutting-edge technologies in terms of neuromorphic devices (artificial synapses and memristors) and pressure-induced emission. This review highlights the fundamentals, the current progress and the remaining challenges for each application, aiming to provide a comprehensive overview of the development status and a navigation of future research for metal halide perovskite materials and devices. [ABSTRACT FROM AUTHOR]

The development of inorganic hole‐transporting materials (HTMs) is one of the most reliable ways to improve the stability of perovskite solar cells (PSCs). However, the un‐optimal buried interfacial contacts and the defects located at the inorganic HTMs/perovskite interface restricted the device's performance. Herein, a phase‐pure CuScO2 has been synthesized and further employed as mesoporous HTM in inverted PSCs. Surprisingly, a facile pretreatment of the hole‐transport layer by a formamidine salt compensates the I− vacancy of the buried perovskite film, thus regulating the interfacial band energy alignment between the HTM and perovskite. This ion compensation strategy can not only in situ repair the ion loss and improve the built‐in electric field, but also decrease the charge injection barrier and suppress the non‐radiative interfacial recombination. Benefiting from these merits, the resulting methylammonium‐free (MA), Cs/FA‐based PSCs displays a power conversion efficiency (PCE) of 22.42% along with excellent thermal and light stability. Moreover, the pre‐buried treatment strategy can be extended to MA‐containing CsFAMA triple‐cation perovskite film, and a champion inverted device delivers a PCE of 23.11%. This study offers a new avenue to the rational design of HTMs for highly efficient and stable PSCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mg2+ doped CuCrO 2 (M:CCO) is synthesized for improving the intrinsic stability of PSCs. • A bilayer mesoscopic HTL (c-NiO x / mp -M:CCO) is constructed to address the interface contact issues. • The novel structure features well-matched energy levels, reduced reflectivity and carrier transport barrier. • The light absorption and kinetics of photo-generated carriers have been decoupled in details. • The proposed strategy enables 21.64% efficiency with excellent photo- and thermal stability. Exploitation of novel inorganic hole-transport materials (HTM) is one of the most promising approaches that achieve stable and efficient perovskite solar cells (PSCs). However, the low conductivity and large carrier transport barriers of the commonly used HTMs/perovskite system severely limit the device performance. Herein, Mg2+ doped CuCrO 2 (M:CCO) nanocrystals are synthesized using a hydrothermal method and further adopted as the HTM for inverted PSCs. The hole conductivity of CuCrO 2 is substantially enhanced upon ion doping. To address the anode/perovskite interfacial contact issues, the resultant M:CCO is designed to be a mesoporous structure atop an ultrathin compact NiO x film (5 nm). This mesoscopic structured bilayer hole-transport layers (HTLs) with well-matched graded energy levels effectively shorten the charge transport pathway, reduce carrier transport barrier in HTL/perovskite interface, and improve the light harvesting efficiency. Combined with the design of a top electron-transport layer and the usage of methylammonium (MA)-free perovskites, a champion PCE of 21.64% has been achieved, which is among the highest efficiencies for inverted MA-free, cesium/formamidinium-based PSCs to date. Moreover, the unsealed device shows excellent long-term stability: more than 91% and 80% of their initial efficiencies were retained after light soaking under 1 sun illumination for 400 h and thermal aging at 85 °C for 1000 h, respectively. This study provides a potential strategy for developing highly efficient and stable inverted PSCs. [ABSTRACT FROM AUTHOR]

Current–voltage hysteresis of perovskite solar cells (PSCs) has raised the concern of accurate performance measurement in practice. Although various theories have been proposed to elucidate this phenomenon, the origin of hysteresis is still an open question. Herein, the use of guanidinium cation (Gu+)‐dopant is demonstrated to tailor the crystal structure of mixed‐cation formamidinium‐cesium lead triiodide (FA0.83Cs0.17PbI3) perovskite, resulting in an improved energy conversion efficiency and tunable current–voltage hysteresis characteristic in planar solar cells. Particularly, when the concentration of Gu‐dopant for the perovskite film increases, the normal hysteresis initially observed in the pristine PSC is first suppressed with 2%‐Gu‐dopant, then changed to inverted hysteresis with a higher Gu‐dopant. The hysteresis tunability behavior is attributed to the interplay of charge/ion accumulation and recombination at interfaces in the PSC. Furthermore, compared to the cell without Gu+‐dopant, the optimal content of 2% Gu+‐dopant also increases the device efficiency by 14%, reaching over 17% under one sun illumination. A new method to control current–voltage hysteresis of planar structured FA0.83Cs0.17PbI3 perovskite solar cells (PSCs) is presented while enhancing device efficiency through tailoring the crystal structure of the perovskite compound with a guanidinium cation (Gu+)‐dopant. New insights into the correlation of the dynamics of device hysteresis with the interfacial charge recombination and accumulation in the PSCs are revealed. [ABSTRACT FROM AUTHOR]