Structural and Functional Insights into Metal-Free Perovskites

Abstract

In the past three years, metal-free perovskites have garnered significant interest as promising candidates for utilization in next-generation wearable electronics. A variety of different molecular structures for these perovskites have been designed for different applications. However, there is still no systematic understanding that can elucidate the relationship between the structural details and properties of perovskites. This would provide a helpful guide for designing a metal-free perovskite with the desired packing structure and properties. Herein, we summarize recently reported structural and functional insights into metal-free perovskites. The underlying design of the molecular structure and its role in the packing structure and resulting properties are explained. In addition, important factors and challenges in the design of a molecular structure that will be useful for future applications are discussed. This information will help enrich the library of potential structures and future applications of metal-free perovskites, which is believed to be much larger than is currently known.

PF6− Pseudohalides Anion Based Metal‐Free Perovskite Single Crystal for Stable X‐Ray Detector to Attain Record Sensitivity

“…Recently, hydrogen bonds formed by the halogen atoms have been noticed in MFPs for their sufficient specificity and strength. [22] Especially, the strongly electronegative F-containing pseudohalides (e.g., BF 4 − , PF 6 − ) have been tentatively used to replace the X-site halides and to achieve the modulation of ferroelectricity, thermoelectric properties, and photophysical properties of MFPs materials. [23,24] More importantly, Choi et al recently demonstrated that by using PF 6…”

Metal‐Free Perovskites for X‐Ray Detection

“…It needs a larger cuboctahedral space and an X-site anion to maintain a 3D framework structure. [17] Additionally, the doping of A-site anion can also change structure and lattice expansion. Still, it has less effect on the stability of the structure and retains its original structure because of the symmetry mismatch.…”

“…To measure the ionic radius of the A-site, a definition method was adopted that uses half of the distance between the two farthest atoms as the ionic radius. [17] However, it is a persistent challenge to accurately predict effective ionic radii in MFPs due to the presence of hydrogen atom rotation around the carbon atom and hydrogen-bonding interactions. [26] These factors can affect the structure of the material and make it difficult to accurately calculate the τ or the μ value that determine the stability of the material.…”

Ag/HfOx/Pt Unipolar Memristor for High-Efficiency Logic Operation

“…After the completion of the SET process, the memristor maintains the LRS with a slope of 1.06. The conduction process under HRS can be described well by the space charge-limited current (SCLC) mechanism: − where J , V , d , and m are the current density, bias voltage, thickness of the functional layer, and fitting index, respectively. The three ranges with different slopes correspond to the small voltage area of ohmic ( m = 0; I ∼ V ), Child’s square ( m = 1; I ∼ V 2 ), and current steep increase ( m > 1; I ∼ V 2 ) ranges.…”