All-inorganic cesium lead halide CsPbX₃ (X = Cl, Br, I) perovskite materials emerged as a rising star in the area of optoelectronics since 2015, due to its excellent photoelectric properties and environmental stability. Substantial progresses were made in the application of many electronic and optoelectronic devices, which attracted wide attention from the scientific community. This paper mainly reviews the latest research progress of cesium lead halide perovskite based planar heterojunction LED, where the structure and working principle of LED devices are briefly introduced. In addition, the classification and summarization of some optimization strategies for improving luminescence performance and working stability of LED devices are emphatically suggested, and the development trend of stable and efficient inorganic perovskite based planar heterojunction LED is finally prospected.

All inorganic perovskite (CsPbX₃) nanocrystals has wide applications in the field of optoelectronic devices due to its excellent photoelectric characteristics, however, stability is still the bottleneck restricting its development. Combining with the current research progress, the BN/CsPbX₃ composite nanocrystals phosphors was synthesized via all-solid-state reactions. During the process, parameters of ball milling, ratio of reactants and other reaction conditions were optimized, thus the BN/CsPbX₃ composite nanocrystals can be stable in the air for more than 60 days. Its luminescence wavelength can cover the range of 417-680 nm with full width at half maximum of 23-47 nm, showing high color purity, and was further used in white LED with high stability and luminance. After placed in the atmosphere for a month, the attenuation of LED luminance is only about 0.7%, and less than 4% deterioration was observed after continuous work of 2 h, showing great working stability.

Perovskite-layer structured (PLS) piezoelectric ceramics have the characteristics of ultra high Curie temperature and good thermal stability, thus PLS ceramics have become one of the hot topics in the field of high temperature piezoelectric ceramics. The present article reviews the research progress on PLS piezoelectric ceramics from the aspects of crystal structure, processing technologies, doping modifications, and forming solid solutions in order to overcome their disadvantages of poor sinterability and low piezoelectricity. Meanwhile, this review summarizes and compares the effects of processing technologies and doping modifications on the sinterability and piezoelectricity of PLS ceramics. Furthermore, the origin of the spontaneous polarization of PLS ferroelectircs is briefly described. The mechanism of ferroelectric phase transition and the approaches to improvement of piezoelectric properties for PLS piezoelectric ceramics are proposed for research work in the near future.

Organic-inorganic hybrid halide perovskites have attracted a huge amount of research interest and arised new research upsurge due to its broad absorption range, low trap density, low carrier recombination, and other excellent optoelectronic properties. Perovskite solar cells have shown great potential for application with maximum power conversion efficiencies evolving from 3.8% to 22.1% in just a few years. Single crystal has extremely low defect density and minimal interface defect than polycrystalline materials. Several research groups successfully cultivated large-sized perovskite single crystals, finding that perovskite single crystal is an ideal material for design and fabrication of photovoltaic devices for better light-response than polycrystalline and thin-film materials. Among all kinds of perovskite materials, CH₃NH₃PbI₃ is one of the most widely studied and applied perovskite materials. This paper reviews the study of CH₃NH₃PbI₃ single crystal recently, introducing its structure and superior characteristics. Particularly, growth methods and applications of perovskite single crystals are highlighted. Finally, the development trend of perovskite single crystals is prospected.

A self-designed traveling zone melting method was employed to fabricate perovskite CsPbBr₃ crystals, which is helpful for impurities removing and moisture excluding. A large-size CsPbBr₃ crystal with a dimension of ϕ 25 mm× 60 mm is successfully obtained. The as-grown crystal shows orange color and displays an excellent transmittance of 78.6% in the range of 600 nm - 2000 nm wavelength. It is revealed by DSC analysis that there is phase transition at 88.1℃ and 131.25℃, respectively. The band gap E_g of the crystal is calculated to be 2.25 eV. The above results prove that the traveling zone melting method is indeed a potential approach for large size and high quality CsPbBr₃ crystal preparation.

La₂NiMnO₆ (LNMO) double-perovskite ceramics are normally prepared by the conventional pressureless sintering technique, which is difficult to produce dense structure and usually needs high sintering temperature as well as long sintering period. In this study, highly-dense La₂NiMnO₆ ceramics with good performance were prepared by a novel Plasma Activated Sintering (PAS) method. The influence of PAS parameters, including sintering temperature and pressure, on crystalline phase, microstructure, relative density and dielectric properties of the LNMO ceramics were systematically studied by the means of XRD, SEM, Archimedes method, and impedance analyzer. The results showed that the crystallinity and grain size of the LNMO ceramics increased with the increase of sintering temperature, but the impurity phases might emerge if the sintering temperature further increased above 1000 ℃. The sintering pressure had little effect on crystalline phase, while the relative density of the LNMO ceramics could be effectively enhanced with the sintering pressure increasing. LNMO ceramics in single orthorhombic structure with relative density of 92% and giant dielectric constant (~10 ⁶) were successfully obtained at the optimum PAS conditions, i.e., sintering temperature of 975-1000 ℃ and sintering pressure of 80 MPa. Compared to the traditional pressureless sintering, LNMO ceramics with dense structure could be obtained by PAS at a relative lower sintering temperature (reduced by 400-500 ℃) with a shorter sintering period (reduced by 2-20 h), which should be attributed to the coupling effect of temperature and stress as well as activation during the sintering process.

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) film is commonly used as hole transport layer in planar perovskite solar cells (PSCs). To further strengthen the charge transport within PEDOT:PSS film and boost the growth of the perovskite crystal on PEDOT:PSS film, carbon nanotubes (CNTs) and dimethyl sulfoxide (DMSO) were simultaneously used as additives to prepare the co-modified film of CNT-DMSO-PEDOT:PSS. Results demonstrate an advantageous cooperative effect of CNTs and DMSO on the co-modified film. The dispersed CNTs with a grid-like structure throughout PEDOT:PSS matrix plays dual roles: to promote the perovskite crystal growth on co-modified surface and to reduce the sheet resistance of the co-modified film, while DMSO improves the conductivity of the co-modified film and controls the loss of CNTs from the co-modified film. Due to the cooperative effect, co-modified film is significantly more capable to collect, transport charges and enhance the perovskite layer growth with larger grains on its surface than that with pristine PEDOT:PSS film or PEDOT:PSS films modified by a single additive of CNT or DMSO, CNT-PEDOT:PSS or DMSO-PEDOT:PSS. Meanwhile, the co-modified film maintains high transparency with a transmittance of 88.8% at 550 nm. As a result, the PSCs of co-modified film has a hig power conversion efficiency of 5.75% in contrast to the devices based on the CNT-PEDOT:PSS (3.01%), DMSO-PEDOT:PSS (2.03%) and pristine PEDOT:PSS (1.30%) films.

TiO₂ is frequently used as electron transport layer in perovskite solar cells, and its structure can directly affect the performance of MAPbBr₃ solar cells. It is necessary to investigate the structural effect of TiO₂ to further understand the working mechanism of such kind solar cells. TiO₂ thin films with different morphology were prepared by spin coating, and MAPbBr₃ (MA = CH₃NH₃) thin films were further deposited on it through anti-solvent assisted crystallization approach. Then, energy band alignment between TiO₂ and MAPbBr₃ were characterized by X-ray photoelectron spectroscopy (XPS). According to the experimental results, TiO₂ with different morphology possessed different electronic structures and yield different band alignment after contacting with MAPbBr₃ perovskite layer. The difference of conduction band value between TiO₂ and MAPbBr₃ can directly affect the transport and collection feature of electrons, thereby governing the performance of the photovoltaic device.