No abstract

Metal halide perovskite light-emitting diodes (PeLEDs) have been regarded as alternative candidates for full-color display applications with rapid progress to surge the external quantum efficiencies (EQEs) over 20%. However, in contrast to the high efficiencies of green, red, and near-infrared PeLEDs, the performance of their blue cousins is still lagging behind, especially the pure-blue one. Obtaining blue perovskite films with negligible nonradiative recombination loss and high stability is of great importance to realize efficient and spectrally stable blue PeLEDs. In this work, through partially replacing the toxic lead ions (Pb2+) with ecofriendly strontium ions (Sr2+) to tune the emission wavelength along with using passivation strategies, all-inorganic pure-blue perovskite films with a high photoluminescence quantum yield of 60.7% were achieved, which then delivered PeLEDs with a luminance of 510 cd m–2 and an EQE of 1.43%. The device yields a record radiance among the most efficient PeLEDs at 467 nm. In addition, the resultant PeLEDs displayed exceptional spectral stability during the electrical bias operation. Our work provides a promising avenue to develop environmentally friendly perovskite materials for efficient and spectrally stable pure-blue PeLEDs and beyond.

Balanced charge injection is key to achieving perovskite light-emitting diodes (PeLEDs) with a low efficiency roll-off at a high brightness. The use of zinc oxide (ZnO) with a high electron mobility as the charge transport layers is desirable; however, photoluminescence (PL) quenching of a perovskite on ZnO always occurs. Here, a quasitwo-dimensional perovskite on ZnO is explored to uncover the PL quenching mechanism, mainly ascribed to the deprotonation of ammonium cations on the ZnO film in association with the decomposition of low-dimensional perovskite phases. Surprisingly, crystal planedependent PL quenching results indicate that the deprotonation rate strongly correlates with the crystal orientation of the ZnO surface. We developed a strategy for suppressing perovskite PL quenching by incorporating an atomic layer deposited Al 2 O 3 onto the ZnO film. Consequently, an efficient inverted PeLED was achieved with a maximum external quantum efficiency of 17.7% and a less discernible efficiency roll-off at a high current density.

We present a design approach to realizing a desired collimated planar incoherent light source (CPILS) by incorporating lenticular microlens arrays (LMLAs) onto the substrates of discrete white organic light-emitting diode (WOLED) light sources and demonstrate the effectiveness of this method in collimated light beam shaping and luminance enhancement simultaneously. The obtained collimated WOLED light source shows enhanced luminance by a factor of 2.7 compared with that of the flat conventional device at the normal polar angle and, more importantly, exhibits a narrowed angular emission with a full-width at half-maximum (FWHM) of ∼33.6°. We anticipate that the presented strategy could provide an alternative way for achieving the desired large scale CPILS, thereby opening the door to many potential applications, including LCD backlights, three-dimensional displays, car headlights, and so forth.

Implementation of ammonium halides to trigger low-dimensional perovskite formation has been intensively investigated to achieve blue perovskite light-emitting diodes (PeLEDs). However, the general roles of the incorporated ammonium cations on...