Fabricating CsPbX₃-Based Type I and Type II Heterostructures by Tuning the Halide Composition of Janus CsPbX₃/ZrO₂ Nanocrystals

Abstract

Fabricating CsPbX3-based heterostructures has proven to be a feasible way to tune their photophysical properties. Here, we report the successful fabrication of Janus CsPbX3/ZrO2 heterostructure nanocrystals (NCs), in which each CsPbX3 NC is partially covered by ZrO2. According to the band alignment, CsPbBr3/ZrO2 and CsPbI3/ZrO2 can be indexed as type I and type II composites, respectively. The type I composites display great enhancement in photoluminescence quantum yield (from 63 to 90%) and photoluminescence lifetime (from 12.9 to 66.1 ns) because of the charge carrier confinement and passivation effect provided by ZrO2. In contrast, the type II composites can be used in photocatalytic reduction of CO2 because electrons and holes are effectively separated and accumulated in ZrO2 and CsPbI3, respectively, under irradiation. Janus CsPbBr3/ZrO2 NCs showed a stability much higher than that of pristine CsPbBr3 against polar solvent treatment. A stable and highly efficient light-emitting device with luminous efficiency up to 55 lm W–1 is fabricated by using CsPbBr3/ZrO2 NCs as the green light source. This work may not only enrich the family of surface-passivated perovskite materials but also provide a good example for the rational design of specific composites in the metal halide perovskite field.

Unravelling the Photocatalytic Behavior of All-Inorganic Mixed Halide Perovskites: The Role of Surface Chemical States

“…9 By tuning the chemical composition of the NCs, harnessing band engineering approaches, both the light harvesting and relative positions of valence and conduction bands (VB and CB, respectively) are controlled. 10,11 Therefore, the photo-oxidation and/or photo-reduction abilities of these materials can be maximized. The band engineering mediated by chemical composition has been useful to improve the photocatalytic (PC) properties of earth-abundant insulators such as BaSO 4 by incorporating Ba-vacancies.…”

Ceramic-like stable CsPbBr3 nanocrystals encapsulated in silica derived from molecular sieve templates

“…A routine strategy is to coat the NCs with inert shells or incorporate them into barrier matrixes, which can isolate CsPbX 3 NCs from moisture and oxygen, and also prevent ion migration and the induced inter-particles fusing 9 . For example, the stabilities of CsPbX 3 NCs have been improved by encapsulating them into inorganic oxides (SiO 2 10 , Al 2 O 3 11 , SiO 2 /Al 2 O 3 12 , TiO 2 13 , ZrO 2 14 ), mesoporous materials (mesoporous silica 15 , metal − organic frameworks 16 ), polymer matrixes (polystyrene 17 , polymethyl methacrylate 18 , polyvinylidene fluoride 19 ), inorganic salts (NaNO 3 20 , NH 4 Br 21 ), and shell formation (CsPbBr 3 / CsPb 2 Br 5 22 , CsPbBr 3 /Cs 4 PbBr 6 23 , CsPbBr 3 /Rb 4 PbBr 6 24 ). However, these shells or barrier matrixes can only slow down the degradation of CsPbX 3 NCs by the external environmental factors, and their stability is still much worse than the ceramic phosphors.…”

Perovskite Nano‐Heterojunctions: Synthesis, Structures, Properties, Challenges, and Prospects

“…This in situ transformation method was also proved successfully for the preparation of CsPbX 3 /ZrO 2 nano‐heterojunctions from Cs 4 PbBr 6 NCs and zirconium (IV) tert ‐butoxide (Zr(OC 4 H 9 ) 4 ). [ 90 ]…”

“…A typical example is the CsPbBr 3 –ZrO 2 nano‐heterojunction. [ 90 ] Like the band structure of the perovskite–insulator heterojunctions, when the perovskite is excited, the excitons intend to be confined within the perovskite. This electron structure can yield enhanced PL intensity, life time, and stability.…”

“…Due the relatively high CB of typical perovskite semiconductors of CsPbX 3 and MAPbX 3 , they can form type‐II heterojunctions with many wide‐bandgap semiconductors, such as TiO 2 , ZnO, ZrO 2 , etc. [ 90,194,195 ] In these heterojunctions, the photo‐generated electrons in perovskite are transferred to the hetero semiconductor part with the holes left, leading to efficient charge carrier separation. Based on this property, the first perovskite‐sensitized solar cells were fabricated upon the MAPbX 3 (X = Br/I)–TiO 2 nano heterojunctions.…”