In this work, we investigate the effects of three different sulfur-containing additives, particularly ethylene sulfate (or 1,3,2dioxathiolane-2,2-dioxide (DTD)), 1,3-propane sultone (1,3-PS) and ethylene sulfite (ES) on the cycling and high temperature storage performance of high-voltage LiCoO 2 and artificial graphite electrodes. These additives process the different sulfur-containing functional groups and exhibit different performance, so that the impacts of changes to the functional group on the electrochemical behavior are interesting to study. Our aim is to understand the relationships between functional groups of these kinds of additives and their roles in improvement of the electrochemical and storage performance of the electrodes. The results clearly indicate that three additives are involved in film-formation on the surface of LiCoO 2 and graphite. Among them, CEI (cathode electrolyte interphase) films formed by DTD and 1,3-PS covered on cathode are thin and stable, thus they can cause a significant improvement of cycle performance in high voltage LiCoO 2 . Also, the SEI film happened in anode of graphite formed by DTD can deliver a good performance at low temperature. On the contrary, the CEI or solid electrolyte interphase (SEI) films formed by ES are not dense and unstable. Therefore it is detrimental to the cycle performance at room, low and elevated temperature.

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The metal halide perovskite nanocrystal (MHP-NC), an easy-to-fabricate and low cost fluorescent material, is recognized to be among the promising candidates of the color conversion material in the micro light-emitting diode (micro-LED) display, providing that the stability can be further enhanced. It is found that the water steam, oxygen, thermal radiation and light irradiation—four typical external factors in the ambient environment related to micro-LED display—can gradually alter and destroy the crystal lattice. Despite the similar phenomena of photoluminescence quenching, the respective encroaching processes related to these four factors are found to be different from one another. The encroaching mechanisms are collected and introduced in separate categories with respect to each external factor. Thereafter, a combined effect of these four factors in an environment mimicking real working conditions of micro-LED display are also introduced. Finally, recent progress on the full-color application of MHP-NC is also reviewed in brief.

Lead-halide perovskite nanocrystals (PNCs), especially those composed of iodine, suffer from degradation problems. Water vapor, oxygen, light, and heat can damage PNCs and consequently quench their photoluminescence (PL). Thus, robust...

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applications, [6] X-ray detectors, [7] potential color conversion layers in visible light communication, [8,9] and mini and micro light-emitting diode (mini-and micro-LED) displays. [10][11][12] Among them, the CsPbI 3 processes the lowest bandgap, which attracts a vast interest from the community. [13] It absorbs the largest portion of solar light in solar-cells, compared to its counterparts; [14] it emits the deepest red light, constituting the largest gamut in the micro-LED display; [12,15] however, it is the least stable member of the lead-halide PNCs family. In addition to the degradation induced by external factors, which are shared among all PNCs, [11] the CsPbI 3 suffers undesirable intrinsic phase transition when the temperature is changing. So far, four phases of CsPbI 3 have been identified. They fall into two categories. The first category, being of the perovskitetype and fluorescently active, contains three phases: α (cubic), β (tetragonal), and γ (orthorhombic) phases. These three phases are collectively denoted as "black" phases. On the contrary, the second category, the "yellow" phase -δ-CsPbI 3 (non-perovskite type), is fluorescently inactive, due to its indirect bandgap. In ambient room temperature (RT), it has been proven that the γ-CsPbI 3 exhibits the highest stability among three black phases, but is still less stable than the thermodynamically favored δ-CsPbI 3 . [16] Phase transitions can be observed at changing temperature, as sketched in Figure 1. At 1 atm, the CsPbI 3 exists in the form of α phase when the temperature is higher than 320 °C, but this critical temperature depends on the pressure. [17] Upon cooling, the CsPbI 3 PNCs either turn directly into δ phase, in the case when no constraint or pressure is exerted, [17,18] as sketched in the Route (1) in Figure 1, or into β and γ phases in succession and temporarily maintains in black phase at RT, in cases where there exist constraints of proper degree [17,19] or crystal grains are sufficiently small, [4] as sketched by Route (2) in Figure 1, but under some triggers, such as environmental humidity in ambient, the meta-stable γ-CsPbI 3 would eventually turn into δ-CsPbI 3 (Route (3), Figure 1). [13,17,20] During heating, if starting from the yellow phase at RT, the δ-CsPbI 3 phase turns to α-CsPbI 3 when the temperature approaches the range from 300 to 450 °C (route (4), Figure 1). [17,[21][22][23] If starting from the black phases at RT (commonly γ-CsPbI 3 ), although it would end up α-CsPbI 3 at temperatures beyond 300 °C, according to literature published, the γ-CsPbI 3 will first transfer to δ-CsPbI 3 This work combines the high-temperature sintering method and atomic layer deposition (ALD) technique, and yields SiO 2 /AlO x -sealed γ-CsPbI 3 nanocrystals (NCs). The black-phase CsPbI 3 NCs, scattered and encapsulated firmly in solid SiO 2 sub-micron particles, maintain in black phases against water soaking, ultraviolet irradiation, and heating, exhibiting remarkable phase stability. A new phase-transition route, from γ via β to α ...

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