Active area scaling enables high operational stabilities and extreme brightness

As the threshold for stimulated emission is significantly reduced at cryogenic temperatures, cooling of perovskite light emitting diodes (PeLEDs) is considered an essential strategy for reaching injection lasing in perovskite diodes. In this work, we demonstrate the intense electrical pulsing of a PeLED stack up to a few kA cm−2 at cryogenic conditions. A high external quantum efficiency (EQE) of 2.9% at 1 kA cm−2 and a radiance >1.95 × 105 W Sr−1 m−2 are achieved when exciting the device with 250 ns electrical pulses at 77 K, showing three times enhancement in comparison with room temperature operation. Furthermore, we provide a comprehensive understanding on how the ion distribution can affect the PeLED characteristics and show that ion motions can be manipulated at cryogenic conditions. This opens new routes for novel material and device designs for further improving PeLED performance.

Following the rapid rise of organic metal halide perovskites towards commercial application in thin film solar cells, inorganic alternatives attracted great interest with their potential of longer device lifetime due to the stability improvement under elevated temperatures and moisture ingress. Among them, cesium lead iodide (CsPbI3) has gained significant attention due to similar electronic and optical properties to methylammonium lead iodide (MAPbI3), with a band gap of 1.7 eV, high absorption coefficient and large diffusion length, while also offering the advantage of being completely inorganic, providing a higher thermal stability and preventing material degradation. On a device level however, it seems also essential to replace organic transport layers by inorganic counterparts to further prevent degradation. In addition, devices are mostly fabricated by spin coating, limiting their reproducibility and scalability; in this case, exploring all-evaporated devices allows to improve the quality of the layers and to increase their reproducibility. In this work, we focus on the deposition of CsPbI3 by CsI and PbI2 co-evaporation. We fabricate devices with an allinorganic, all-evaporated structure, employing NiO and TiO2 as transport layers, and evaluate these devices for both photodetector and solar cell applications. As a photodetector, low leakage current, high EQE and detectivity, and fast rise and decay times were obtained; while as a solar cell, acceptable efficiencies were achieved. These all-inorganic, all-evaporated devices represent one step forward towards higher stability and reproducibility, while enabling large area-compatibility and easier integration with other circuitry and, in future, the possible commercialization of perovskite-based technology.