Abstract：Lead halide perovskite， as a new class of optoelectronic materials， has demonstrated excellent optical and electrical properties， extensive and important applications in solar cells， light-emitting diodes， photodetectors， lasers and so on， attracting great attention. Rare earth is a special kind of material in the periodic table of elements，ranging the elements from 57 to 71， with 4fn and 4f n-15d electronic configurations. What kind of new baby will be born if rare earth combines with perovskite materials and devices？ This paper aims to combine the author's work and experience in related fields， briefly review the progress made in this field in recent years， and search for the problems and challenges faced in the future. This article is not to summarize the complex individual phenomenon to be brief， but to explore the common problems of universal significance for the purpose. In the selection of data and information， it may be biased， and there is a serious suspicion of “Every potter praises his pot”， please think carefully.
Abstract：Mn2+ is one of the most important activator ions in the family of luminescent materials. Whether as doped ions or raw materials of the host， it can improve the luminescence performance of halide perovskite. However， the driving force of the synthesis has changed， as well as the luminescence stability. This is because the binding energy and formation energy have changed， along with the thermal stability and environmental stability. The luminescence mechanism of Mn2+ ions is relatively distinct. Exciton emission of the host and self-trapped emission （STE） caused by transient photo-induced defects may also participate in the luminescence mechanism. In this review， we will summarize the luminescence of different types of structures of Mn2+ doped halide perovskites or Mn2+ based halide perovskites， focusing on the doping driving force and doping strategy of Mn2+ ions.
Abstract：In recent years， all-inorganic perovskite quantum dots （QDs） have attracted extensive attention from researchers due to their excellent photoelectric properties， but their poor stability greatly limits their applications. By using the stability of glass， the perovskite QDs are controlled to in-situ growth inside the glass matrix， so that the glass coats around the perovskite QDs. And the contact between QDs and the external environment is cut off， thus effectively improving the stability of QDs. By doping specific ions in perovskite QD-embedded glass， the crystallization of QDs and their luminescence peak can be controlled. Besides that， a new luminescence center can be introduced. In this paper， the research progress of ion-doped perovskite QD-embedded glass is comprehensively introduced according to the purposes of ion doping， which provides ideas and references for the recent research on ion-doped perovskite QD-embedded glass.
Abstract：Perovskite solar cells（PSCs） have undergone unprecedented rapid development in the past decade. A certified power conversion efficiency （PCE） of 25.7% has been achieved， which is comparable to that of commercialized silicon solar cells. However， the inferior stability under heat and moisture has hindered their commercial application. Two-dimensional （2D） or quasi-2D perovskite materials have attracted considerable interest due to their superior structural and environmental stability in comparison with their 3D counterpart. The organic spacers play a very important role in 2D perovskites and they could directly affect the optoelectronic properties of the materials and the PCE of the devices. The organic spacers for 2D PSCs mainly include aliphatic spacers and aromatic spacers. The aromatic spacers have received more and more attention because of their large dielectric constants， superior charge transport properties and tunable self-assembly structures. In this review， we systematically summarize the effects of aromatic spacers on the structural and optoelectronic properties of 2D perovskite materials， and their applications in 2D PSCs.
Keywords：two-dimensional perovskite;solar cell;stability;charge transport
Abstract：At present， promoting the transition of the energy industry to a system that is effective， clean， and flexible has currently emerged as the key to tackling the world's environmental issues. The progress of the Internet of Things and the technology revolution have created a new demand to combine solar equipment and cells into a single component in order to collect energy in a wider range of application situations. Flexible perovskite solar cells（FPSCs） based on flexible polymers such as polyethylene terephthalate （PET） and polyethylene naphthalate（PEN） have emerged as a rising star in the third generation of solar cells in the past decade due to their high energy conversion efficiency， high flexibility， low preparation cost and certain portability. In addition， it has a natural affinity for environmentally friendly and economically beneficial roll-to-roll manufacturing technology which will enable it to play a key role in the development of flexible self-powered electronic products， large-scale building integrated photovoltaic（BIPV） and space aerospace. In this review， we emphatically discuss the critical role and briefly summarize the most recent developments of the flexible transparent conductive substrate， low-temperature processed charge transporting layer， and mechanically resilient perovskite film in single and tandem FPSCs. Finally， combined with the large-scale manufacturing technology of FPSCs， we offer some insight into the reliability and operational stability of the package and discuss potential practical applications in large-area modules and so forth.
Keywords：flexible;perovskite solar cell;flexible perovskite tandem solar cell;photovoltaic module
Abstract：Lead-halide perovskite single-crystal （SC） X-ray detectors have received considerable attentions due to their strong stopping power and high carrier transport efficiency. However， the application of lead-halide perovskite for wearable electronics is inhibited by their toxicity. ABX3 hybrid perovskites have versatile structures， which enable the combination of optoelectronic properties and environmentally friendly processing through B-site engineering. In this perspective， we summarize the state of the art in perovskite SC X-ray detectors， providing an overview of B-site engineering from lead-based to lead-free and then metal-free. Later， perspective for future perovskite wearable electronics are proposed. We hope that this perspective will provide a helpful guide for structure design towards highly efficient and eco-friendly perovskite wearable electronics.
Abstract：Dominating X-ray detectors are mainly divided into direct semiconductor X-ray detectors and indirect scintillator X-ray detectors. In recent years， hybrid X-ray detectors have emerged by combing the advantages of semiconductors and scintillators. The mixed semiconductors and scintillators as active layers lead to different working mechanisms. The charge/energy transfer between the two phases avoids the afterglow effect of the scintillator. And the presence of scintillators also optimizes the properties of the semiconductor material. The review summarizes the mechanism， progress， and synergistic effect of hybrid X-ray detectors to highlight the advances of hybrid X-ray detectors. Three types of hybrid X-ray detectors are discussed in detail according to different working mechanisms and their respective characteristics. Finally， we present an outlook on hybrid X-ray detectors’ limitations and the future development direction.
Abstract：A facile ligand-assisted solution process was proposed to synthesize quasi-2D CsPbBr3 perovskite nanoplatelets （NPs） with ultrapure green photoluminescence （PL） at room temperature. The as-synthesized CsPbBr3 NPs exhibit an ideal emission peak at 526 nm with a narrow FWHM of 16 nm and a high photoluminescence quantum yield （PLQY） of 87%. As a green downconverter， the CsPbBr3 NP shows a CIE coordinate at （0.145， 0.793） and covers 91% of the Rec. 2020 standard in the CIE 1931 color space， which was much better than that of all the present green phosphors. Moreover， a WLED was successfully fabricated based on these ultrapure green light-emitting CsPbBr3 NPs， which exhibits a luminous efficiency 39 lm/W with a CIE （0.33， 0.29） under a 20 mA driving current.
Keywords：CsPbBr3 perovskite;nanoplatelets;ultrapure green photoluminescence;WLED
Abstract：All-inorganic zero-dimensional （0D） metal halides， owing to their intriguing optical properties and easy solution processibility， are emerging as a new generation of luminescent materials and as an alternative to lead halide perovskites for various applications such as solid-state lighting and photodetectors. Herein， a new yellow phosphor is developed based on Cd2+-doped Cs2ZnCl4， which exhibits intense broadband and long-lived （11.4 ms） photoluminescence （PL） at 565 nm upon 270 nm excitation， with a PL quantum yield up to 46.0%. Temperature-dependent PL spectroscopic analyses reveal that the broadband PL originates from the forbidden 3E→1A1 transition of Cd2+. Specifically， localized exciton emission is observed at low temperatures below 170 K， in parallel with efficient energy transfer from the localized excitons to Cd2+. Besides， the phosphor displays an excellent anti-thermal quenching property， remaining 90% PL intensity at 150 ℃ in comparison with that at room temperature. These findings provide not only new insights into the excited-state dynamics of Cd2+ in metal halides， but also a new avenue for the exploration of novel and efficient luminescent materials based on 0D metal halides.
Abstract：Cu（Ⅰ）-based metal halides， as a new generation of environment-friendly luminescent materials， have attracted extensive attention. Herein， a novel zero-dimensional Cu（Ⅰ）-based metal halide （C12H24O6）NaCuBr2 was prepared by solution assisted crystallization method. Under 365 nm excitation， （C12H24O6）NaCuBr2 single crystal exhibits ultra-broadband orange red emission with the full width at half maximum of 346 nm and the photoluminescence quantum yield of 42.6%. Theoretical calculation and experimental studies on the low temperature and excitation-dependent emission spectra show that the ultra-broadband emission peaking at 700 nm is derived from the formation of a degenerate energy level by the interaction between the 3d orbital of the Cu+ ion and the 4p orbital of the Br- ion. At low temperature， the degeneracy of the energy level is reduced due to the lattice distortion， and the emission peak at 700 nm is split into two emission peaks at 629 nm and 735 nm， respectively. In addition， the electron is excited to a higher energy level of S3 for （C12H24O6）NaCuBr2 under high energy excitation， which corresponds to the emission peak at 480 nm observed at 77 K. The white light-emitting diode （LED） device prepared using （C12H24O6）NaCuBr2 possesses a color rendering index as high as 90.6， indicating their potential application in the field of full-spectrum lighting.
Keywords：Zero-dimensional structure;Cu-based metal halides;full-spectrum lighting
Abstract：Zero-dimensional （0D） hybrid metal halides with tunable self-trapped exciton （STE） emissions are promising for lighting and displaying applications. In particular， 0D hybrid metal halides with dual-band emissions arising from singlet and triplet STEs have potentials in white-light solid-state lighting. Herein， two 0D hybrid antimony chlorides， （C24H20P）2SbCl5 （Ⅰ） and （C24H20P）2SbCl5⋅H2O⋅0.5DMF（Ⅱ） （C24H20P = tetraphenylphosphonium， Ph4P） are reported. The compounds Ⅰ and Ⅱ exhibit single broadband red and yellow emissions upon low-energy （LE） photons （e.g. 360 nm） excitation， respectively， arising from their triplet STEs. In addition， upon high-energy （HE） photons （e.g. 310 nm） excitation， the compound Ⅱ shows a dual-band emission with an additional blue emission band deriving from singlet STEs， exhibiting a warm-white emission. Intriguingly， a reversible phase transformation between Ⅰ and Ⅱ is achieved through a dynamic insertion and extraction of DMF and water molecules. This work unravels the effect of small molecules on the crystalline structures and the conversion between single- and dual-band emission properties in 0D antimony halides， which could guide the design of 0D hybrid metal halides for sensor applications.
Abstract：In the device structure of metal halide perovskite light-emitting diodes （Pero-LEDs）， the hole transport layer （HTL） is one of the critical factors affecting the efficiency of Pero-LEDs. Because cobalt acetate （Co（OAc）2） film has excellent photoelectric properties， it has been selected as the HTL for green Pero-LEDs. However， the pure cobalt-based HTL films have problems such as poor carrier transport ability and large film roughness. Therefore， in this paper， by introducing the organic small molecule additive ethanolamine （ETA）， the proportion of Co3+/Co2+ in the transport layer is effectively regulated， and the conductivity of the transport layer is improved. At the same time， the addition of ETA can slow down the crystallization process of HTL precursor solution during the annealing process， bringing in a transport layer film with lower roughness， which is conducive to the deposition of high-quality perovskite films. Based on the doped Co-based HTL films， the optimal device brightness reaches 45 207 cd/m2， and the maximum external quantum efficiency （EQE） reaches 15.08%， proving that the Co-based compound is a novel HTL with good device performance.
Keywords：Perovskite LEDs;Co（OAc）2;Ethanolamine;Hole Transport Layer;doping
Abstract：Recently， the emerging ternary copper-based halide （CsCu2I3） materials have attracted much attention in the application of environmentally friendly light-emitting diodes （LEDs） due to their high photoluminescence quantum yield （PLQY）， non-toxicity， good stability， and low cost. However， the synthesis of high-quality CsCu2I3 light-emitting films is still a great challenge due to the ungovernable crystallization dynamics of the CsCu2I3， which limits the further improvement of device performance. Here， by using a mixed solvent of toluene and methanol as an antisolvent to improve the pinning effect from the antisolvent， increasing the nucleation density of CsCu2I3 crystals， and reducing the grain size of the films， a smooth and dense CsCu2I3 nanocrystalline film was formed. Moreover， the mixed antisolvent strategy can effectively enhance the radiative recombination efficiency and significantly improve the PL properties of the CsCu2I3 films. Compared with the control sample（only using toluene）， the PLQY of the films prepared by the mixed antisolvent method is increased by 1.5 times， and the exciton binding energy was increased from ~201.6 meV to ~234.5 meV. Finally， the maximum luminance and the external quantum efficiency of the CsCu2I3 LED based on the mixed antisolvent strategy were enhanced by 5.5 times and 1.6 times compared with the control device， respectively. The results of this work are not only conducive to deepening the understanding of crystallization laws during the preparation of CsCu2I3 films， but also help to further promote the device performance of CsCu2I3-based environmentally friendly LEDs.
Keywords：CsCu2I3;nanocrystalline films;anti-solvent;yellow LED