High Stability and Temperature‐Dependent Photoluminescence of Orthorhombic CsPbI₃ Perovskite Nanoparticles

Abstract

High thermal stability of all‐inorganic perovskite nanocrystals (NCs) offers their potential application in various fields such as solar cells and light‐emitting diodes. However, the cubic cesium lead iodide (α‐CsPbI3) with the most appropriate bandgap for light harvesting is thermodynamically unstable at room temperature and spontaneously transforms into the undesired orthorhombic δ‐CsPbI3. Here, a simple method is demonstrated to synthesize orthorhombic γ‐CsPbI3 NCs using 3‐aminopropyl triethoxysilane molecules as capping ligands. The crystalline structure and morphology of these γ‐CsPbI3 NCs hardly change after exposure to ethanol even though they are capped with fewer ligands. Their high stability is also demonstrated by retaining their photoluminescence (PL) intensity after heating/cooling cycles in the range of 295–375 K, in contrast to a quick destruction of α‐CsPbI3 NCs under the same condition. More importantly, temperature‐dependent PL spectra reveal that the exciton/electron–phonon coupling and exciton recombination process of these γ‐CsPbI3 NCs strongly depend on their particle sizes. This finding may enable versatile design of stable γ‐CsPbI3 NCs with different sizes meeting diverse demands for various applications.

Porphyrin Functionalization of CsPbBrI2/SiO2 Core–Shell Nanocrystals Enhances the Stability and Efficiency in Electroluminescent Devices

“…Two observations were evident, the emission peak shifted to lower energies upon cooling the sample and the full width at half maximum (FWHM) exhibited a maximum at 290 K. The shift arises due to the thermal compression of the lattice and an increased interaction between lead and halides, resulting in a broadening of states at the valence band edge which reduces the size of the band gap, this is consistent with previous reports on perovskites. [ 21,22 ] Further, as the FWHM of the PL signal is phonon‐dependent and typically increases with temperature FWHM∝exp{ E LO /( k B T )} −1 , a necessity of the decrease in broadening with higher temperature is a phase transition. Tang et al have investigated the electron–phonon coupling of different perovskite phases and their temperature dependent behavior.…”

Stable and Efficient Red Perovskite Light-Emitting Diodes Based on Ca 2+ -Doped CsPbI 3 Nanocrystals

“…As a result, ion migration and crystal fusion easily occur in the solid state, which leads to increasing the size of CsPbI 3 NCs. The enlarged size of CsPbI 3 must induce phase transition [ 14 , 53 , 54 ]. Benefitting from small-sized Ca 2+ doping, the increase in τ should improve the phase stability of CsPbI 3 .…”

Remarkable Black‐Phase Robustness of CsPbI3 Nanocrystals Sealed in Solid SiO2/AlOx Sub‐Micron Particles

“…These three values, even the one of pristine sample, approach the levels of those carried out for ligand-covered CsPbI 3 NCs in a vacuum chamber, which fell between 85% to 88% after heating to 102 °C (375 K). [51] The AlO x ALD can be processed under a wide range of temperature, from 40 to 300 °C, and the elevated temperature leads to more condensed layer and higher barrier effect. [52] On the other hand, however, because of the existence of pure water as oxygen source during ALD processing, the high temperature may also pose detrimental effects on CsPbI 3 NCs during processing.…”