Centimeter‐Sized Single Crystals of Two‐Dimensional Hybrid Iodide Double Perovskite (4,4‐Difluoropiperidinium)₄AgBiI₈ for High‐Temperature Ferroelectricity and Efficient X‐Ray Detection

Abstract

Ferroelectricity and X‐ray detection property have been recently implemented for the first time in hybrid bromide double perovskites. It sheds a light on achieving photosensitive and ferroelectric multifunctional materials based on 2D lead‐free hybrid halide double perovskites. However, the low Tc, small Ps, and relatively low X‐ray sensitivity in the reported bromide double perovskites hinder practical applications. Herein, the authors demonstrate a novel 2D lead‐free iodide double perovskite (4,4‐difluoropiperidinium)4AgBiI8 (1) for high‐performance X‐ray sensitive ferroelectric devices. Centimeter‐sized single crystal of 1 is obtained and exhibits an excellent ferroelectricity including a high Tc up to 422 K and a large Ps of 10.5 μC cm−2. Moreover, due to a large X‐ray attenuation and efficient charge carrier mobility (μ)–charge carrier lifetime (τ) product, the crystal 1 also exhibits promising X‐ray response with a high sensitivity up to 188 μC·Gyair−1 cm−2 and a detection limit below 3.13 μGyair·s−1. Therefore, this finding is a step further toward practical applications of lead‐free halide perovskite in high‐performance photoelectronic devices. It will afford a promising platform for exploring novel photosensitive ferroelectric multifunctional materials based on lead‐free double perovskites.

A multifunctional molecular ferroelectric with chiral features, a high Curie temperature, large spontaneous polarization and photoluminescence: (C9H14N)2CdBr4

“…When the temperature rises to 410 K (higher than T c ), the shape of the P – E hysteresis loop becomes round rather than straight due to leakage current, which indicates that 1 loses ferroelectricity. 15 At the same time, we tested the polarization hysteresis loop of 150–200 K, which also shows an ideal rectangle (Fig. S9, ESI † ).…”

“…The inherent characteristic of ferroelectrics is switchable spontaneous polarization. 15 In order to verify the switchable spontaneous polarization of compound 1 , we first measured the local lateral PFM phase and amplitude on the surface of the single crystal sample thin film in the 400 nm × 400 nm region. As shown in Fig.…”

“… 8–10 Although great progress has been made in research into ferroelectrics in the last ten years, the combination of ferroelectric materials and practical applications makes high-temperature phase transition materials more ideal, 11 such as DIPAX (DIPA = diisopropylaminium; X = Cl, Br, ClO 4 − ) ( T c = 426 K); 12 hexane-1,6-diammonium pentaiodobismuth (HDA-BiI 5 ) ( T c = 380 K) which has the highest phase transition temperature and the narrowest band gap ( E g = 1.89 eV); 13 [( R )- N -(1-phenylethyl)ethane-1,2-diaminium]PbI 4 ( T c = 378 K); 14 and (4,4-difluoropiperidinium) 4 AgBiI 8 ( T c = 422 K). 15 Lead-free metal halides have been widely studied in photoelectric and photovoltaic fields. For example, Sn, Sb, Cd and Bi ions can be used to replace Pb ions, and can also show excellent photoluminescence and ferroelectric properties, 16–18 such as [(C 3 H 5 ) 2 N(CH 3 ) 2 ] 2 SnCl 6 which shows excellent semiconductor and photoluminescence properties.…”

Lead-Free Perovskite Single Crystals: A Brief Review

“…The detection of X-ray has been of great importance due to the wide applications of X-ray in various fields, and some relevant works are summarized in Table 4 on this topic. [73][74][75][76]. Liu et al developed MA 3 Bi 2 I 9 SCs, showing large X-ray absorptivity, large bulk resistivity of around 4.7 × 10 10 ohm-cm, high density of ~4.1 g/cm 3 , and high ion migration activation energy of 0.83 eV [77].…”

Lead-Free BiFeO3–BaTiO3 Ceramics: An Overview

“…In case of inorganic perovskite oxides, transition elements, or an element from IVA or VA group are at B-site A site is occupied by alkaline earth metal or an alkali metal [20]. The tolerance factor is used for the determination of structural and thermal stability and is given by the formula [21]:…”