Organometal halide perovskites (MHPs) are widely used in energy harvesting as well as energy storage applications due to their superior optoelectronic properties. However, structural, optical, and electronic properties of these materials are strongly dependent on the halide substitution. So far methylammonium lead tri‐bromide‐perovskite‐based supercapacitors have shown an energy density in the range of 10–15 Wh kg−1. Therefore, further optimization is needed to improve the energy storage efficiency in halide perovskite‐based supercapacitors. It has been observed that the charge storage capacity increases with the increasing ionic conductivity in the perovskite active layer. Herein, a series of porous electrodes are prepared to optimize ionic conductivity by mixing powders of different halide‐based perovskite single crystals for supercapacitor application. It has been demonstrated that maximum efficiency is achieved for a specific bromide composition to iodide ratio with an energy density of ≈22 Wh kg−1 and a power density of 600 W kg−1. The ionic conductivity is improved at least by two orders to 3.2 × 10−13 m2 s−1 in the mixed halide sample than pure halide perovskites, while charge transfer resistance is decreased to 40.5 Ω cm−2. However, overall device stability and Coulombic efficiency decrease with the increasing iodide content.
Highly fluorescent cesium lead‐based (CsPbX3, X═Br, Cl, I) inorganic metal halide perovskites semiconductors have gained immense popularity in the last decade due to the economic and straightforward fabrication techniques involved in these materials along with their excellent electrical and optoelectronic properties. Cesium lead halide nanocrystals are well known for their fluorescence in the visible region with extremely high internal quantum efficiencies; thus making them highly suitable for the fabrication of efficient light‐emitting diodes, transistors and photodetectors. Although perovskite nanocrystals (NCs) are more fluorescent compared to their bulk counterpart, there have been very few reports on the synthesis and characterization of CsPbX3 perovskite NCs. In this work, we have synthesized and investigated the CsPbBr3 and CsPbBr2I NCs to understand the fundamental optoelectronic properties and structural integrity in mixed halide perovskite NCs. We have estimated ~10 nm average particle size of CsPbBr3 nanocrystals from the high‐resolution transmission electron microscopy (HRTEM) while CsPbBr2I has ~16 nm average particle size with slightly higher polydispersity. Most interestingly, we do not observe any phase segregation of bromide and iodide ions in mixed halide perovskite quantum dots due to finite size effect. This is also confirmed by the energy dispersive X‐ray spectroscopy (EDS) mapping data. However, CsPbBr3 nanocrystals are relatively more stable than the mixed halide perovskite nanocrystals due to fewer defects. Anomalous behavior is observed in the photoluminescence intensity with the variation of precursor concentration indicating a complex nature nanoparticle synthesis.
2D-perovskites are generally more stable than 3D perovskites while charge transport in 2D-perovskites becomes inefficient. On the other hand, the instability of 3D perovskite films under heat, light and environmental...
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