A semiconducting molecular ferroelectric with a bandgap much lower than that of BiFeO3

Abstract

Ferroelectrics have been attracting increasing attention as good candidates for multifunctional materials because of their fascinating properties. However, their large bandgap has been a roadblock limiting their application in optoelectronics and photovoltaics, among other applications. Hybrid ferroelectrics have the potential to combine the advantages of both molecular materials and ferroelectrics. In this context, we designed a hybrid ferroelectric: (2-(ammoniomethyl)pyridinium)SbI 5 . It shows an above-room-temperature Curie temperature (T c = 360 K), a large spontaneous polarization (P s = 4 μC cm − 2 ) and a small bandgap (2.03 eV) that is much smaller than the recently reported 2.7-3.65 eV for the lead-halide perovskite ferroelectrics. The implementation of ferroelectricity in hybrid semiconducting materials may be a feasible way to realize high-performance ferroelectric optoelectronic and photovoltaic devices. NPG Asia Materials (2017) 9, e342; doi:10. 1038/am.2016.193; published online 20 January 2017 INTRODUCTIONIntensive research on photovoltaic (PV) materials over the past six decades has been driven by the increasingly serious energy crisis. Among the emerging PV technologies, hybrid perovskite solar cells demonstrate extraordinary power conversion efficiencies and very low cost. 1-5 The high power conversion efficiency (up to 20.1%) is because of the strong light absorption and high carrier mobility of hybrid perovskites. Nevertheless, much work needs to be done to overcome their instability in moisture and the toxicity of lead. Thus, researchers have begun to explore related materials with a lower toxicity and/or better stability. [6][7][8] Meanwhile, the past few years have seen the renaissance of photoferroelectric materials for PV applications. [9][10][11][12] Photoferroelectric materials, such as BiFeO 3 and SbSI, are semiconducting ferroelectrics that show both photosensitive and ferroelectric properties. They adopt a newly described mechanism known as the anomalous PV effect, where photogenerated electrons and holes are directly separated by the spontaneous electric field from the intrinsic ferroelectric polarization, resulting in an open circuit voltage above the bandgap. However, the power conversion efficiency of conventional inorganic ferroelectrics remains low because of the poor light absorption ability that is limited by their large bandgaps.Organic-inorganic hybrid ferroelectrics have the potential to combine advantages from both hybrid materials and ferroelectrics. We recently demonstrated that photoferroelectricity can be achieved in lead-halide perovskite-type ferroelectrics. 13,14 Although these compounds show excellent ferroelectricity, they have two drawbacks: a relatively high bandgap (42.7 eV) and toxicity from the Pb element.

Designing and Constructing a High‐Temperature Molecular Ferroelectric by Anion and Cation Replacement in a Simple Crown Ether Clathrate

“…Most reversible phase transition will accompany by the thermal anomaly behaviors. [40][41][42][43][44][45] For af irst order phase transition, there exists latent heat during the phase transition process, whereas forasecond phaset ransition, specific heat capacity (C p )i sa pparently different aroundt he phase transition. Therefore, we carried out the differential scanning calorimetry( DSC) measurement by TA-Instruments DSC TA2000 instrumen.…”

Will organic–inorganic hybrid halide lead perovskites be eliminated from optoelectronic applications?

“…2), which may be a long journey before the nal commercialization of PSCs. 7,[35][36][37][38][39] Therefore, this review focuses on the research progress on inorganic lead-free perovskites and their application in photovoltaics in recent years, with the aim to clarify the development of the existing problems.…”

High‐Temperature Reversible Phase‐Transition Behavior, Switchable Dielectric and Second Harmonic Generation Response of Two Homochiral Crown Ether Clathrates

“…As molecular reversible phase transition materials were continuously discovered, higherr equirementsa re focusedo nt he exploration of high molecular phase transition temperature and multiple functional molecular materials (such as SHG responses, chirality) because of their excellentp erformance and practicality.I nspiringly,anew class of compounds, namely the crown ether clathrates has attracted great attentioni nr ecent years. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] These clathrates tend to form a" stator-rotor" configuration with protonated organic amine cations and deprotonated inorganic acid anions. [17][18][19][20][21] When the temperature changes,t he protonated organic aminec ation often acts as a rotor and undergoes slightt orsion or order-disorder change, sometimes the crown ether rings may also undergo order-disorder rotation, therebyi nducing the reversible phase transition.…”