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In this work, Zn 2 SnO 4 : x Cr3+ with high near-infrared luminescence intensity (broad emission centered at 800 nm and sharp emission at 703 nm) were successfully prepared by high temperature solid state method. Measurements indicated that the samples exhibited obvious photoluminescence as well as persistent luminescence properties. The results of X-ray diffraction indicated that high temperature facilitated the entry of Cr3+ into the Zn 2 SnO 4 crystal lattice and formed replacement doping and promoted the luminescence efficiency of the samples. And, under the condition of 1450 °C and 0.002 at% Cr3+ concentration, sample with optimum NIR fluorescence properties was prepared. In the high-temperature sintering process, many defects of Zn 2 SnO 4 were generated, which effectively promoted the formation of vacancies. The energy levels of these lattice defects (trap energy levels) facilitated the sub-stable trapping of electrons and produce afterglow properties. Analysis of luminescence mechanism reveals that the broad emission band centered at 800 nm and the sharp emission peak at 703 nm were derived from the energy level transitions of 4T 2 (4F)→4A 2 and 2E→4A 2 of Cr3+, respectively. Though, the long afterglow luminescence duration of Zn 2 SnO 4 :Cr3+ needs to be further improved compared with gallate-based NIR phosphors, Zn 2 SnO 4 :Cr3+ do have a promising application in bio-imaging due to its special NIR emission range. • Zn 2 SnO 4 :Cr3+ with high NIR luminescence intensity was synthesized successful. • The effect of preparation conditions on PL and afterglow properties was clarified. • The NIR emission of Zn 2 SnO 4 :Cr3+ derives from the 2E.→4A 2 and 4T 2 (4F)→4A 2 transitions of Cr3+. [ABSTRACT FROM AUTHOR]

Cuprous(Ⅰ) iodide (CuI) is widely used as a conducting material in various optoelectronic devices. However, defect properties and instabilities lead to changes in the semiconductor properties of CuI, which seriously affects the stability of related optoelectronic devices. Therefore, in this paper, the decomposition and defect state properties of CuI films are investigated in depth. CuI was prepared by a simple iodination method and belongs to the zinc blende type structure, preferentially crystallizing along the (111) direction. Microscopic tests reveal that grains in CuI film are tightly bonded without obvious cracks or holes, and the grain size reaches 1.231 μm. In the subsequent spectral analysis, multiple emission peaks (free exciton and defect emission peak) were obtained by Gaussian fitting. The two major point defects (Cu vacancy (V Cu) and I vacancy (V I)) in CuI were analyzed theoretically, and the calculated defect energy levels matched the energies of the emission peaks. The results of Gaussian waveform fitting and density functional calculations indicate the presence of V Cu defects and V I defects in CuI. Significant variations in emission and electrical properties were observed in successive tests, indicating the relatively poor long-term stability of the CuI samples. The changes in the emission characteristics are mainly manifested by the weakening of the 416 nm emission and the enhancement of the 720 nm emission, while the changes in the electrical characteristics are mainly manifested by the increasing resistance. The above changes are attributed to the concentration of defect states, mainly due to the increase of V I defects and the decrease of V Cu defects, hence the severe iodine decomposition occurs in the CuI samples. To inhibit the decomposition, three schemes (multiple iodination, multilayer iodination, and encapsulation) were proposed, and relevant experiments were conducted. • Study on the relationship between the optoelectronic properties of CuI and semiconductor defects. • Demonstrated the presence of iodine decomposition in CuI samples. • Methods to inhibit the decomposition of CuI were investigated. [ABSTRACT FROM AUTHOR]

In recent years, there have been numerous reports on the inter-transformation between non-luminous Cs 4 PbX 6 nanocrystals (NCs) and luminous CsPbX 3 nanocrystals (NCs). However, most of these reports have focused on the transformation between Cs 4 PbBr 6 NCs and CsPbBr 3 NCs, with little attention given to Cs 4 PbCl 6 NCs. This paper aims to address this gap by investigating the formation of Cs 4 PbCl 6 through the addition of excess CsCl during thermal evaporation. The presence of Cs 4 PbCl 6 was found to passivate the CsPbCl 3 film and improve its luminescence. The highest photoluminescence (PL) intensity of the sample was observed when the ratio of PbCl 2 to CsCl was 1:1.17. This can be attributed to the enhanced crystal quality and reduced non-radiative recombination resulting from the presence of Cs 4 PbCl 6. Furthermore, rapid annealing led to a two-fold increase in the PL intensity of the film. Notably, the film containing Cs 4 PbCl 6 exhibited excellent thermal stability, maintaining a constant PL intensity within the annealing temperature range of 200°C–300 °C. This can be attributed to the prevention of grain size growth in the film due to the presence of Cs 4 PbCl 6. Finally, the electroluminescent device test results showed that the electroluminescence intensity reached the highest at 6 V driving voltage, which was caused by the effective carrier recombination, while the ratio of PbCl 2 to CsCl was 1:1.17 and the annealing temperature was 180 °C. This study provided a novel approach to enhancing the photoelectric performance of CsPbCl 3. • CsPbCl 3 perovskite film is prepared by thermal evaporation method, and CsPbCl 3 /Cs 4 PbCl 6 mixed film is obtained by adding excess CsCl. • The film maintains violet/blue emission at 409 nm, and the full width at half maximum is only 12 nm, showing excellent monochromaticity. • Photoluminescence intensity is nearly twice the original value at a PbCl 2 to CsCl ratio of 1:1.17. • Annealing can also improve the performance of the film, and the film has good stability under low temperature (200°C–300 °C) annealing conditions. • The presence of an appropriate quantity of Cs 4 PbCl 6 enhances the performance of photoinduced and electro-induced devices of CsPbCl 3 thin films. [ABSTRACT FROM AUTHOR]