We are pleased to present to you this special issue dedicated to highlighting recent advances in a class of semiconductors-halide perovskites-which has received considerable recent attention for photonic and optoelectronic applications. Halide perovskites with the general formula of ABX₃ have attracted such attention owing to their remarkable optical and electronic properties as well as solution processability. In the past decade, tremendous efforts have been devoted to fabricating high-performance devices including photovoltaic cells, light-emitting diodes (LEDs), lasers, radiation detectors, etc [1–9]. Although still in the early stages of development, device performance has been approaching and in some cases even exceeding the current state-of-the-art commercial technologies, which reveals a great potential for bringing halide perovskites into practice. The continued investigations in terms of fundamental study and device engineering further provide deep insights into structure-performance relationships, which enable strategies to explore, design, and utilize halide perovskites beyond conventional semiconductor materials. Under this subject, several excellent reviews have been published recently covering numerous important discoveries and progress [10–12].

This special issue is intended to offer a glimpse of the evolving halide perovskites research area, in which we present a collection of reviews and original research articles that deal with representative branches of the field ranging from luminescent materials to optoelectronic devices. Starting from materials, Stratakis et al. [13] successfully synthesized composite perovskite-glasses that exhibit interesting photoluminescent properties, which is very promising for the development of highly stable perovskite materials for lighting and displays. Qian et al. [14] developed a novel mechanosynthesis strategy to improve the luminous performance of CsPbBr₃ powder by embedding into zero-dimensional Cs₄PbBr₆ perovskites, thus leading to enhanced radiative recombination and PLQY. These make it suitable for high-level back-lighting devices. Kopwitthaya et al. [15] reported a scintillator based on rubidium copper chloride, which showed a bright violet emission under ionizing radiation, indicating a potential application in X-ray imaging screens. Steering towards devices, Yang et al. [16] demonstrated efficient all-inorganic perovskite LED employing a KBr-doped hole-transport layer, where KBr can not only improve charge injection, but also suppress interface exciton quenching via defect passivation, which represents a straightforward and efficient way to boost the EL performances of perovskite LEDs. Cloutier et al. [17] showed a facile ambient fabrication of triple cation perovskites for near-infrared light-emitting diodes. The synthesis approach and film tailoring technique described in this work constitutes a significant step towards low-cost and efficient perovskite LEDs. Meanwhile, Basak et al. [18] realized the perovskite-based 1^st order distributed feedback (DFB) lasers for the first time, which exhibit superior edge emission in comparison with well-studied 2^nd order DFB perovskite lasers, making them highly attractive for photonic integration applications. From the review side, Gong et al. [19] provide an overview of current understandings on the mechanical properties and fracture behaviors of perovskites, which are expected to advance the technology of flexible and stretchable solar cells towards a fully stretchable and wearable energy source. Additionally, Demir et al. [20] review vacuum-evaporated perovskite LEDs from the perspective of materials, film deposition and device issues, where they also suggest some guidelines for high-performance devices and offer insight on their prospects for large area applications.

In summary, this special issue showcases the fascinating reviews and research on halide perovskite for photonics and optoelectronics in the past decade. We hope this can attract further attention from other researchers to push this field to the next stage. It has been a great pleasure and honor to edit this special issue. We thank all contributing authors for their excellent contributions. We are very grateful to all the reviewers and the editorial team of Optical Materials Express for their efforts to realize this special issue.