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Next-generation light-emitting applications such as displays and optical communications require judicious control over emitted light, including intensity and angular dispersion. To date, this remains a challenge as conventional methods require cumbersome optics. Here, we report highly directional and enhanced electroluminescence from a solution-processed quasi-2-dimensional halide perovskite light-emitting diode by building a device architecture to exploit hybrid plasmonic-photonic Tamm plasmon modes. By exploiting the processing and bandgap tunability of the halide perovskite device layers, we construct the device stack to optimise both optical and charge-injection properties, leading to narrow forward electroluminescence with an angular full-width half-maximum of 36.6° compared with the conventional isotropic control device of 143.9°, and narrow electroluminescence spectral full-width half-maximum of 12.1 nm. The device design is versatile and tunable to work with emission lines covering the visible spectrum with desired directionality, thus providing a promising route to modular, inexpensive, and directional operating light-emitting devices. By exploiting Tamm plasmon modes, Ooi et al. report highly directional and enhanced electroluminescence in quasi-2D perovskite LEDs with angular FWHM of 36.6° and spectral FWHM of 12.1 nm. The photonic platform is versatile and tuneable across the visible spectral range with directionality up to 40°. [ABSTRACT FROM AUTHOR]

Most thin‐film photovoltaic modules are constructed on soda‐lime glass (SLG) substrates containing alkali oxides, such as Na2O. Na may diffuse from SLG into a module's active layers through P1 lines, an area between a module's constituent cells where the substrate‐side charge transport layer (CTL) is in direct contact with SLG. Na diffusion from SLG is known to cause several important effects in II–VI and chalcogenide solar modules, but it has not been studied in perovskite solar modules (PSMs). In this work, we use complementary microscopy and spectroscopy techniques to show that Na diffusion occurs in the fabrication process of PSMs. Na diffuses vertically inside P1 lines and then laterally from P1 lines into the active area for up to 360 μm. We propose that this process is driven by the high temperatures the devices are exposed to during CTL and perovskite annealing. The diffused Na preferentially binds with Br, forming Br‐poor, I‐rich perovskite and a species rich in Na and Br (Na‐Br) close to P1 lines. Na‐Br passivates defect sites, reducing non‐radiative recombination in the perovskite and boosting its luminescence by up to 5×. Na‐Br is observed to be stable after 12 weeks of device storage, suggesting long‐lasting effects of Na diffusion. Our results not only point to a potential avenue to increase PSM performance but also highlight the possibility of unabated Na diffusion throughout a module's lifetime, especially if accelerated by the electric field and elevated temperatures achievable during device operation. [ABSTRACT FROM AUTHOR]

Perovskite light-emitting diodes (LEDs) have attracted broad attention due to their rapidly increasing external quantum efficiencies (EQEs)1–15. However, most high EQEs of perovskite LEDs are reported at low current densities (<1 mA cm−2) and low brightness. Decrease in efficiency and rapid degradation at high brightness inhibit their practical applications. Here, we demonstrate perovskite LEDs with exceptional performance at high brightness, achieved by the introduction of a multifunctional molecule that simultaneously removes non-radiative regions in the perovskite films and suppresses luminescence quenching of perovskites at the interface with charge-transport layers. The resulting LEDs emit near-infrared light at 800 nm, show a peak EQE of 23.8% at 33 mA cm−2 and retain EQEs more than 10% at high current densities of up to 1,000 mA cm−2. In pulsed operation, they retain EQE of 16% at an ultrahigh current density of 4,000 mA cm−2, along with a high radiance of more than 3,200 W s−1 m−2. Notably, an operational half-lifetime of 32 h at an initial radiance of 107 W s−1 m−2 has been achieved, representing the best stability for perovskite LEDs having EQEs exceeding 20% at high brightness levels. The demonstration of efficient and stable perovskite LEDs at high brightness is an important step towards commercialization and opens up new opportunities beyond conventional LED technologies, such as perovskite electrically pumped lasers.Perovskite LEDs with exceptional performance at high brightness are demonstrated achieving an operational half-lifetime of 32 hours, an important step towards commercialization opening up new opportunities beyond conventional LED technologies, such as perovskite electrically pumped lasers. [ABSTRACT FROM AUTHOR]