It remains a central challenge to the information display community to develop red light-emitting diodes (LEDs) that meet demanding color coordinate requirements for wide color gamut displays. Here, we report high-efficiency, lead-free (PEA)2SnI4 perovskite LEDs (PeLEDs) with color coordinates (0.708, 0.292) that fulfill the Rec. 2100 specification for red emitters. Using valeric acid (VA)—which we show to be strongly coordinated to Sn2+—we slow the crystallization rate of the perovskite, improving the film morphology. The incorporation of VA also protects tin from undesired oxidation during the film-forming process. The improved films and the reduced Sn4+ content enable PeLEDs with an external quantum efficiency of 5% and an operating half-life exceeding 15 hours at an initial brightness of 20 cd/m2. This work illustrates the potential of Cd- and Pb-free PeLEDs for display technology.

Metal halide perovskite absorbers with wide bandgaps (1.6−1.7 eV) that are suitable for tandem devices typically require high Br concentrations; this renders the material prone to halide segregation and degradation. Inorganic, bromine-free CsPbI3 has a wide bandgap of 1.7 eV and does not suffer from halide segregation; however, these active layers are not stable at room temperature. Here, we report a method to create stable tetragonal perovskites with a bandgap near 1.7 eV: we add small amounts of large A-site cations having ionic radii between 272 and 278 pmdimethylammonium (DMA) and guanidinium (Gua)into the crystal lattice. When we deploy perovskites using mixed Cs and these large organic cations, we achieve stable, wide bandgap perovskites with power conversion efficiencies of 15.2% and V OC of 1.19 V. This study extends materials selection for wide bandgap Cs-based perovskites.

Halide perovskites have been shown to be promising materials in making light‐emitting diodes. At present, almost all of perovskite materials are made by solution‐based synthesis. There are very limited reports on fabricating perovskite LEDs by vapor‐phase deposition (VPD), a method that can be easily scaled up for commercial production. In this paper, dual‐source VPD is used to fabricate stable CsPbBr3 perovskite thin films with excellent luminescent properties. Scanning electron microscope and atomic force microscope studies show that CsPbBr3 films, when coated with a thin LiBr overlayer, demonstrate an extraordinary mass transport at room temperature to re‐assemble into well‐defined islands. LiBr is also shown to passivate nonradiative defects and boost photoluminescence performance of the CsPbBr3, improving the intensity by a factor of 11 for a nominal 18 nm perovskite film and leading to extremely narrow photoluminescence peaks (16 nm FWHM). This self‐assembled perovskite LED shows major improvement in the electroluminescence performance, almost tripling the brightness of reference devices. X‐ray photoelectron spectroscopy measurement shows that surface LiBr improves Cs/Pb chemical stoichiometry, reduces Br vacancies, and shift the Fermi energy level toward conduction band minimum.

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In today's manufacturing of organic light-emitting diode on silicon for microdisplay technologies, a top-emitting OLED (TEOLED) is required to be fabricated on top of an active-matrix circuitry located on the silicon backplane. This requires a highly reflective anode to enhance the luminance output. However, during the production process of a TEOLED, the hole injection efficiency and electrical conductivity may be suppressed by environmental exposure, in particular, moisture and oxygen. Given this, aluminum is an unfavorable reflective anode due to the primary concern of its native insulating oxide layer. The native oxide tends to grow during the patterning of the metal anode. In this paper, we have discovered that, by utilizing an Al2O3/MoO3 heterojunction anode structure, a highly efficient device can be made to achieve a current efficiency of 94 cd/A at a luminance of 1000 cd/m2. X-ray/ultraviolet photoelectron spectroscopy measurements show the formation of molybdenum gap states and favorable energy level alignment for hole injection.