Abstract
Hybrid organic–inorganic perovskites providing integrated functionalities for multimodal switching applications are widely sought-after materials for optoelectronics. Here, we embark on a study of a novel pyrrolidinium-based cyanide perovskite of formula (C4H10N)2KCr(CN)6, which displays thermally driven bimodal switching characteristics associated with an order–disorder phase transition. Dielectric switching combines two features important from an application standpoint: high permittivity contrast (Δε′ = 38.5) and very low dielectric losses. Third-order nonlinear optical switching takes advantage of third-harmonic generation (THG) bistability, thus far unprecedented for perovskites and coordination polymers. Structurally, (C4H10N)2KCr(CN)6 stands out as the first example of a three-dimensional stable perovskite among formate-, azide-, and cyanide-based metal–organic frameworks comprising large pyrrolidinium cations. Its stability, reflected also in robust switching characteristics, has been tracked down to the Cr3+ component, the ionic radius of which provides a large enough metal–cyanide cage for the pyrrolidinium cargo. While the presence of polar pyrrolidinium cations leads to excellent switchable dielectric properties, the presence of Cr3+ is also responsible for efficient phosphorescence, which is remarkably shifted to the near-infrared region (770 to 880 nm). The presence of Cr3+ was also found indispensable to the THG switching functionality. It is also found that a closely related cobalt-based analogue doped with Cr3+ ions displays distinct near-infrared phosphorescence as well. Thus, doping with Cr3+ ions is an effective strategy to introduce phosphorescence as an additional functional property into the family of cobalt-cyanide thermally switchable dielectrics.
Highlights
Hybrid organic−inorganic perovskites (HOIPs) have generated tremendous attention due to their unique physicochemical properties, which can be tailored by prudent choice of organic and inorganic components.[1−5] Much publicity has grown around those materials that exhibit coexistence of two or more functional properties in one phase; multiple functionalities can be harnessed to perform more than one task at the same time.[6−8] coupling between different physicochemical properties may lead to emergent phenomena, enabling construction of new types of multifunctional devices.[9,10]
We demonstrate for the first time the third-harmonic generation (THG) switching for HOIP material, taking Pyr2KCr(CN)[6] as a model
Despite the fact that THG occurs in any crystalline solid, THG switching has never been reported for HOIP materials
Summary
Hybrid organic−inorganic perovskites (HOIPs) have generated tremendous attention due to their unique physicochemical properties, which can be tailored by prudent choice of organic and inorganic components.[1−5] Much publicity has grown around those materials that exhibit coexistence of two or more functional properties in one phase; multiple functionalities can be harnessed to perform more than one task at the same time.[6−8] coupling between different physicochemical properties may lead to emergent phenomena, enabling construction of new types of multifunctional devices.[9,10] Prime examples of such multifunctionality in the broad perovskite family are three-dimensional (3D) lead halides exhibiting optoelectronic, photovoltaic, and nonlinear optical (NLO) properties.[2,3,5,11] Multifunctionality, is not confined only to classic lead halide HOIPs; multifunctional properties were reported for a number of 3D perovskites composed of metal centers linked by multiatomic ligands such as HCOO−, H2POO−, or N(CN)2−. Www.acsami.org worth noting that in order to better understand the relationship between the structure and optical properties of the cyanides comprising Pyr+ cations, we report an optical study of the previously discovered nonperovskite cobalt analogue Pyr2KCo(CN)[6] doped with Cr3+ ions.
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