Aqueous Phase Exfoliating Quasi‐2D CsPbBr₃ Nanosheets with Ultrahigh Intrinsic Water Stability

Abstract

All-inorganic cesium lead halide (CsPbX 3 , X = Cl, Br, and I) perovskite nanocrystals (NCs) have gained increasing attention in recent years, due to their excellent optical and electronic properties that are critical in the fabrication of efficient optoelectronic [1] and photovoltaic devices. [2] Currently, the external quantum efficiency (EQE) of perovskite light-emitting diodes (LEDs) has exceeded 20% [1d,e] while the perovskite solar cells have recently reached a power conversion efficiency (PCE) of 23.7%. [3] However, the major obstacle to future commercialization of perovskite NCs is their inherent vulnerability due to their ionic nature. [4] Therefore, perovskite NCs will decompose fast when exposed to ambient, especially in the presence of water or even in a moist environment. [5] But the appearance of water is inevitable during the process of materials synthesis and devices fabrication, which will badly influence the device stability and performance. So, the intrinsic water stability improvement of all-inorganic perovskite plays a key role to effectively enhance the long-time stability of perovskite materials and enormously promote the commercial applications of perovskite-based optoelectronic and photovoltaic devices.To overcome the poor water stability of perovskite NCs arising from their intrinsically high ionic character, many strategies have been developed. Typically, the substitution of the more stable ligands for the commonly used oleic acid (OA) and oleylamine (OLA) can suppress the degradation and maintain the crystal structures in water or other polar solvent. [6] In addition, polymer materials can effectively encapsulate perovskite NCs and avoid them directly contact with the external environment, which ensure the high environment stability especially superior water resistance of the peovskite-polymer composites. [7] Moreover, embedding perovskite NCs into inorganic matrix such as ionic salt, metallic oxide and silica also can obtain relatively ideal environment stability. [8] Although all of these works remarkably enhance the water stability of perovskite materials, these strategies mainly focus on isolating the materials from the external environment but not intrinsically improving its water stability. And also, these isolated materials will have a negative effect on charge transfer ability. Therefore, to develop the novel perovskite materials with both long-term intrinsic water stability and good charge transport ability is extremely urgent for optoelectronic and photovoltaic devices.All-inorganic cesium lead halide perovskite nanocrystals (NCs) have emerged as attractive optoelectronic materials due to the excellent optical and electronic properties. However, their environmental stability, especially in the presence of water, is still a significant challenge for their further commercialization. Here, ultrahigh intrinsically water-stable all-inorganic quasi-2D CsPbBr 3 nanosheets (NSs) via aqueous phase exfoliation method are reported. Compared to conventional perovskite NCs, these u...

Low‐Dimensional Metal Halide Perovskite Photodetectors

“…To this end, much effort has been made to improve the liquid exfoliation technique, such as ligand/solvent selection and controlled centrifugation, helping produce 2D MHPs with higher quality and better thickness selection. [ 79,80 ]…”

“…To this end, much effort has been made to improve the liquid exfoliation technique, such as ligand/solvent selection and controlled centrifugation, helping produce 2D MHPs with higher quality and better thickness selection. [79,80] Apart from RP type MHPs with layered structure, 2D nonlayered MHP nanostructures were also prepared through various solution-based processes. Similar to the synthesis of MHP NCs, the hot injection method has been applied to produce colloidal 2D MHP NSs.…”

Facial synthesis of highly stable and bright CsPbX3 (X=Cl, Br, I) perovskite nanocrystals via an anion exchange at the water-oil interface

“…It indicates that the treated CsPbBr 3 NCs have a much better water resistance. The improved stability and PLQY could be attributed to the surface passivation after the treatment in the aqueous solution of HBr [17,27,32].…”

“…However, the RT strategy is severely limited by using polar reagents (such as dimethyl sulfoxide (DMSO) or N,Ndimethylformamide (DMF)). These polar reagents, such as DMF, can reduce the stability and efficiency of NCs due to the inherent ionic characteristic of CsPbX 3 [16][17][18]. Typically, CsPbI 3 NCs synthesized at room temperature are easily degraded within a few days, making the RT method not suitable for CsPbI 3 NCs.…”

“…The aqueous solution of HX can also be employed as an active halide source to realize a high-quality anion exchange and obtain highly luminescent CsPbX 3 NCs at the water-oil surface. Furthermore, the water passivation and halogen-rich environment can improve the stability of CsPbX 3 NCs [17,26,27].…”