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Defect suppression via precursor additives is crucial to achieving high efficiency and stable perovskite quantum dot light‐emitting diodes (Pe‐QLEDs). Herein, a strategy using 4‐dodecylbenzenesulfonic acid (DBSA) is developed to simultaneously suppress halide interstitial and vacancy defects by tuning the crystallization process of perovskite quantum dots (Pe‐QDs) through coordinate bonding and chemical circumstance modulation, leading to faster radiative recombination and less carrier accumulation in the device. Meanwhile, the Pe‐QDs with defect suppression demonstrate higher ion migration activation energies. Thanks to the defect suppression strategy with the aid of the alkyl sulfonic group, the obtained Pe‐QDs exhibit an external quantum efficiency (EQE) of up to 20.4% and an operating lifetime of over 100 h in QLED, which is the leading performance of green Pe‐QLEDs. This work provides a strategy from a different aspect for the perovskite QLED field in improving the performance and stability of devices. [ABSTRACT FROM AUTHOR]

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]

Perovskites have showed significant potential for the application in photodetectors due to their outstanding electrical and optical properties. Integrating two-dimensional (2D) materials with perovskites can make full use of the high carrier mobility of 2D materials and strong light absorption of perovskite to realize excellent optoelectrical properties. Here, we demonstrate a photodetector based on the WTe2/CsPbI3 heterostructure. The quenching and the shortened lifetime of photoluminescence (PL) for CsPbI3 perovskite confirms the efficient charge transfer at the WTe2/CsPbI3 heterojunction. After coupled with WTe2, the photoresponsivity of the CsPbI3 photodetector is improved by almost two orders of magnitude due to the high-gain photogating effect. The WTe2/CsPbI3 heterojunction photodetector reveals a large responsivity of 1157 A W−1 and a high detectivity of 2.1 × 1013 Jones. The results pave the way for the development of high-performance optoelectronic devices based on 2D materials/perovskite heterojunctions. [ABSTRACT FROM AUTHOR]

The luminescence thermal quenching (LTQ) behavior is one of the detrimental effects which result in poor stability and hinder the practical applications of luminescent nanocrystals (NCs) severely. Suppressing the LTQ effect is fundamentally important, especially for the recent rising star lead halide perovskite NCs while related investigations are rare. Herein, taking CsPbBr3 NCs with high photoluminescence quantum yield (PLQY) as examples, a surface anchoring mechanism is proposed and the LTQ effect is successfully overcome. By introducing hybrid ligand system with large binding effect and steric hindrance, ligand desorption induces irreversible LTQ effect and the formation of surface atom vibration related transient traps is suppressed. As a result, 96.3% and 75.6% of the initial PL intensity are maintained up to 378 and 423 K, respectively, which are even superior to conventional core–shell NCs. Notably, after being treated under 333 K for 15 days, a PL intensity remnant of >88.4% is achieved. Such anti‐LTQ mechanism is also extended to blue perovskite NCs. Temperature‐tolerant stimulated emission and high temperature lasing phenomenon are fulfilled with considerable thermal stability. This work provides a new mechanism which can possibly help to solve the bottleneck toward practical luminescence applications for perovskite nanostructures. [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]

In recent years, perovskite light-emitting diodes (PeLEDs) have developed rapidly with the highest external quantum efficiency exceeding 20%. Their unbalanced carrier injection and non-radiative recombination assisted by defects lead to the destruction of perovskite crystal structures and poor device stability, which hinders their commercialization process. Thus, to understand the origin of device performance, the key is to figure out the charge-carrier dynamics of the devices. In this review, the charge-carrier dynamics of perovskites are discussed, including radiative and non-radiative recombination, together with the various passivation strategies. Second, we focus on the interfacial carrier dynamics and its influence on device performance. Various strategies to improve the injection balance have been implemented to address the inherent challenges associated with PeLEDs. Last but not least, the characterization techniques of PeLEDs are provided to study the carrier dynamics of PeLEDs. [ABSTRACT FROM AUTHOR]

Halide perovskites have been one of the most promising research hotspots in the optoelectronic field. Recently, the issue of ion migration has been proved to be of great significance to their long-term stability and performance of optoelectronic devices. However, the stability of perovskite Cs2SnX6 (X = I, Br, Cl) under the light or electric field conditions has not been explored. In this work, we reported halide ion migration in lead-free all‐inorganic perovskite Cs2SnX6. The calculated formation energy to some degree reveals the concentration of the halide vacancy, which provides the favorable conditions for halide ion migration. Importantly, the theoretical long-term ion migration barriers are investigated to be higher than 1.00 eV, indicating they are relatively stable compared to CsPbX3, and the computational result matches the experimental result with the Nernst−Einstein relation that we adopted. The halogen ion migration energy barrier is 0.91 eV under the bias of 5 V, indicating that the perovskite Cs2SnX6 is relatively stable under a certain electric field. Furthermore, the experimental comparison of XRD results demonstrate that perovskite Cs2SnX6 has no obvious ion migration under certain light conditions. Finally, the analysis results show the Sn–X bond strength that explains the cause of such high barriers. These results reveal the migration mechanism of halide ions and provide new impetus for their optoelectronic applications. [ABSTRACT FROM AUTHOR]

It is imperative to improve the quality of light absorber and reduce the charge‐carrier recombination for efficient perovskite solar cells (PSCs). Herein, a synergistic regulation strategy that combines the tailoring of crystallinity and construction of multilayer cascade charge transport layers (CTLs) for inverted CsPbI2Br solar cells is presented. The film quality of CsPbI2Br is well tuned via F− doping. In addition, gradient energy alignment between perovskite and CTLs, i.e., NiOx/Zn:CuGaO2/perovskite and perovskite/TiO2/PC61BM/ZnO, favors the charge transfer and depresses carrier recombination. Noticeably, the TiO2 interlayer with deep valence band maximum effectively blocks the hole back‐transfer from perovskite to PC61BM. These unique characteristics of the novel structured CsPbI2Br device give a champion power conversion efficiency (PCE) of 15.10% along with good thermal and operational stability. Moreover, the graded CTLs can be expanded to methylammonium‐free hybrid perovskite device (Eg = ≈1.76 eV) by delivering a PCE of 18.12%, showing great promise in tandem solar cells for use as top cell. [ABSTRACT FROM AUTHOR]

Recently, Kovalenko and co-workers and Li and co-workers developed CsPbX3 (X = Cl, Br, I) inorganic perovskite quantum dots (IPQDs), which exhibited ultrahigh photoluminescence (PL) quantum yields (QYs), low-threshold lasing, and multicolor electroluminescence. However, the usual synthesis needs high temperature, inert gas protection, and localized injection operation, which are severely against applications. Moreover, the so unexpectedly high QYs are very confusing. Here, for the first time, the IPQDs' room-temperature (RT) synthesis, superior PL, underlying origins and potentials in lighting and displays are reported. The synthesis is designed according to supersaturated recrystallization (SR), which is operated at RT, within few seconds, free from inert gas and injection operation. Although formed at RT, IPQDs' PLs have QYs of 80%, 95%, 70%, and FWHMs of 35, 20, and 18 nm for red, green, and blue emissions. As to the origins, the observed 40 meV exciton binding energy, halogen self-passivation effect, and CsPbX3@X quantum-well band alignment are proposed to guarantee the excitons generation and high-rate radiative recombination at RT. Moreover, such superior optical merits endow them with promising potentials in lighting and displays, which are primarily demonstrated by the white light-emitting diodes with tunable color temperature and wide color gamut. [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]

All-inorganic cesium lead halide perovskites have been emerging as the promising semiconductor materials for next-generation optoelectronics. However, the fundamental question of how the environmental atmosphere affects their photophysical properties, which is closely related to the practical applications, remains elusive. Here, we report the dynamic switching between radiative exciton recombination and non-radiative carrier trapping in CsPbBr3 by controlling the atmospheric conditions. Specifically, we show that the photoluminescence (PL) intensity from the CsPbBr3 crystals can be boosted by ~ 60 times by changing the surrounding from vacuum to air. Based on the comprehensive optical characterization, near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) as well as density functional theory (DFT) calculations, we unravel that the physisorption of oxygen molecules, which repairs the trap states by passivating the PL-quenching bromine vacancies, is accountable for the enhanced PL in air. These results are helpful for better understanding the optical properties of all-inorganic perovskites. Perovskite-based optoelectronics are expected to become an important component of devices such as solar cells and light-emitting diodes. However, how they are affected by environmental conditions is still not fully understood. The authors investigate the mechanisms, which occur for inorganic perovskites when in contact with ambient atmosphere and how this could potentially impact upon device performance. [ABSTRACT FROM AUTHOR]

Understanding the glass-like thermal conductivity (κ) in simple-composition crystalline materials is critical for the development and design of low‒ κ materials. Here, we report the origin of glass-like low κ in binary crystalline tantalates RETa 3 O 9 (RE = Nd, Sm, Eu, Gd) by atomistic simulation. It is found that the low κ is mainly due to the rattling effect of RE3+ cations arising from the large difference in the interatomic bonding between O‒RE and O‒Ta. The vibrational mode decomposition results reveal that most modes in RETa 3 O 9 fall in the Ioffe–Regel regime and exhibit a strongly diffusive nature due to the fluctuating interatomic force of O‒Ta in the TaO 6 octahedron. The dual-phonon model reveals that the vast majority (>97%) of heat in RETa 3 O 9 is transported by diffusive modes rather than propagating modes. Consequently, the thermal conduction in RETa 3 O 9 exhibits a unique glass-like nature. Contrary to conventional belief, the optical phonon modes in RETa 3 O 9 play a significant role in thermal conduction. Overall, the new insight into the link between chemical binding and glass-like κ serves to the development and design of low‒ κ materials for thermoelectric and thermal management applications. [Display omitted] [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]

A novel non-noble perovskite-type Ce 1/3 NbO 3 electrocatalyst is proposed as a promising nitrogen rediction reaction by both theoretically prediction and experimentally confirmation. • A Ce 1/3 NbO 3 perovskite is proposed and exhibits a potential N 2 activation ability by the theoretical prediction. • Experimentally, the produced ammonia from the nitrogen reduction reaction (NRR) under such Ce 1/3 NbO 3 electrocatalyst is identified successfully by the electrochemical tests, confirming our theoretical prediction. • The detailed reaction mechanism calculations conclude that NRR proceed by the distal mechanism and the potential determining step is the hydrogenation of *NH 2. Herein, a novel Ce 1/3 NbO 3 perovskite is proposed as an efficient electrocatalyst to catalyze the nitrogen reduction reaction (NRR) at ambient conditions. Density functional theory calculations are firstly used to predict the potential N 2 activation ability of Ce 1/3 NbO 3 , and then, the Ce 1/3 NbO 3 with a flower-like porous structure is prepared by a hydrothermal process and post calcination. Electrochemical tests reveal that such catalyst achieves a high NRR performance with the Faradaic efficiency of 6.87% and NH 3 yield of 10.34 µg h−1 cm−2 at −0.8 V vs RHE in 0.1 M Na 2 SO 4 , keeping up with many electrocatalysts reported recently. The mechanistic studies disclose that Nb atom is favorable as the efficient active site for NRR by the distal pathway, and Ce atom synergistically enhances the charge transfer during the NRR process. Our work provides an important reference to the rational design of the promising electrocatalysts for NRR. [ABSTRACT FROM AUTHOR]