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A perovskite LED with a perovskite film treated under optimum thermal annealing conditions exhibits a significantly enhanced long-term stability with full coverage of the green electroluminescence emission due to the highly uniform morphology of the perovskite film.

All-vacuum-deposited perovskite solar cells produced by controlling reagent partial pressure in high vacuum with newly developed multi-layer electron and hole transporting structures show outstanding power conversion efficiency of 17.6% and smooth, pinhole-free, micrometer-sized perovskite crystal grains.

Three small molecules as front cell donors for tandem cells are thoroughly evaluated and a high power conversion efficiency of 11.47% is achieved, which demonstrates that the oligomer-like small molecules offer a good choice for high-performance tandem solar cells.

Organic–inorganic hybrid perovskites have cemented their position as an exceptional class of optoelectronic materials thanks to record photovoltaic efficiencies of 22.1%, as well as promising demonstrations of light-emitting diodes, lasers, and light-emitting transistors. Perovskite materials with photoluminescence quantum yields close to 100% and perovskite light-emitting diodes with external quantum efficiencies of 8% and current efficiencies of 43 cd A⁻¹ have been achieved. Although perovskite light-emitting devices are yet to become industrially relevant, in merely two years these devices have achieved the brightness and efficiencies that organic light-emitting diodes accomplished in two decades. Further advances will rely decisively on the multitude of compositional, structural variants that enable the formation of lower-dimensionality layered and three-dimensional perovskites, nanostructures, charge-transport materials, and device processing with architectural innovations. Here, the rapid advancements in perovskite light-emitting devices and lasers are reviewed. The key challenges in materials development, device fabrication, operational stability are addressed, and an outlook is presented that will address market viability of perovskite light-emitting devices.

Perovskites have sparked a revolution in photovoltaics, and their excellent optoelectronic properties hold the potential to trigger a similar advance in the field of light emission. The versatility of organic–inorganic hybrid perovskites as emitters and gain media is explored, device performance/architectures, processing conditions, and working mechanisms are analyzed, and the main barriers toward market viability are addressed.

The interfacial microstructure in organic bulk heterojunction solar cells can dictate photovoltaic performance. By controlling the chemical interactions of bulk heterojunction components with specific surfaces, the electrical pathways at interfaces can be precisely varied to achieve suitable electronic properties across such interfaces. This is studied by J. J. Jasieniak and co-workers on page 3944.

Tunneling contacts made of any insulating polymers, a champion technology in silicon solar cells, are shown to increase the stabilized efficiency of perovskite solar cells (PSCs) to 20.3%. The tunneling layers spatially separate photo-generated electrons and holes at the perovskite-cathode interface and reduce charge recombination. The tunneling layers made of hydrophobic polymers also significantly enhance the resistance of PSCs to water-caused damage.

High fatigue resistance, bistability, and drastic property changes among isomers allow efficient modulation of the current output of organic thin-film transistors (OTFTs) to be obtained by a photogating of the charge-injection mechanism.

Mixed Pb–In perovskite solar cells are fabricated by using lead(II) chloride and indium(III) chloride with methylammonium iodide. A maximum power conversion efficiency as high as 17.55% is achieved owing to the high quality of perovskites with multiple ordered crystal orientations.

Organolead halide perovskites are used for low-operating-voltage multilevel resistive switching. Ag/CH₃NH₃PbI₃/Pt cells exhibit electroforming-free resistive switching at an electric field of 3.25 × 10³ V cm^–1 for four distinguishable ON-state resistance levels. The migration of iodine interstitials and vacancies with low activation energies is responsible for the low-electric-field resistive switching via filament formation and annihilation.

Hall effect measurements in CH₃NH₃PbBr₃ single crystals reveal that the charge-carrier mobility follows an inverse-temperature power-law dependence, μ ∝ T^−γ, with the power exponent γ = 1.4 ± 0.1 in the cubic phase, indicating an acoustic-phonon-dominated carrier scattering, and γ = 0.5 ± 0.1 in the tetragonal phase, suggesting another dominant mechanism, such as a piezoelectric or space-charge scattering.

Perovskite oxides are demonstrated for the first time as efficient electrocatalysts for the hydrogen evolution reaction (HER) in alkaline solutions. A-site praseodymium-doped Pr_0.5(Ba_0.5Sr_0.5)_0.5Co_0.8Fe_0.2O_3–δ (Pr0.5BSCF) exhibits dramatically enhanced HER activity and stability compared to Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3–δ (BSCF), superior to many well-developed bulk/nanosized nonprecious electrocatalysts. The improved HER performance originates from the modified surface electronic structures and properties of Pr0.5BSCF induced by the Pr-doping.

Halide perovskites are a rapidly developing class of medium-bandgap semiconductors which, to date, have been popularized on account of their remarkable success in solid-state heterojunction solar cells raising the photovoltaic efficiency to 20% within the last 5 years. As the physical properties of the materials are being explored, it is becoming apparent that the photovoltaic performance of the halide perovskites is just but one aspect of the wealth of opportunities that these compounds offer as high-performance semiconductors. From unique optical and electrical properties stemming from their characteristic electronic structure to highly efficient real-life technological applications, halide perovskites constitute a brand new class of materials with exotic properties awaiting discovery. The nature of halide perovskites from the materials' viewpoint is discussed here, enlisting the most important classes of the compounds and describing their most exciting properties. The topics covered focus on the optical and electrical properties highlighting some of the milestone achievements reported to date but also addressing controversies in the vastly expanding halide perovskite literature.

Halide perovskites are a promising new class of semiconductors that deliver clean energy from inexpensive inorganic materials. Perovskite materials compete in conversion efficiency with classical inorganic semiconductors and promise a bright future toward exploitation of cheap, clean energy resources. Understanding how these materials actually work poses the main challenge in contemporary materials science research.