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Perovskite PbCoO synthesized at 12 GPa was found to have an unusual charge distribution of PbPbCoCoO with charge orderings in both the A and B sites of perovskite ABO. Comprehensive studies using density functional theory (DFT) calculation, electron diffraction (ED), synchrotron X-ray diffraction (SXRD), neutron powder diffraction (NPD), hard X-ray photoemission spectroscopy (HAXPES), soft X-ray absorption spectroscopy (XAS), and measurements of specific heat as well as magnetic and electrical properties provide evidence of lead ion and cobalt ion charge ordering leading to PbPbCoCoO quadruple perovskite structure. It is shown that the average valence distribution of PbCoO between PbCrO and PbNiO can be stabilized by tuning the energy levels of Pb 6s and transition metal 3d orbitals.

Magnetoelectric multiferroics have received much attention in the past decade due to their interesting physics and promising multifunctional performance. For practical applications, simultaneous large ferroelectric polarization and strong magnetoelectric coupling are preferred. However, these two properties have not been found to be compatible in the single-phase multiferroic materials discovered as yet. Here, it is shown that superior multiferroic properties exist in the A-site ordered perovskite BiMn Cr O synthesized under high-pressure and high-temperature conditions. The compound experiences a ferroelectric phase transition ascribed to the 6s lone-pair effects of Bi at around 135 K, and a long-range antiferromagnetic order related to the Cr spins around 125 K, leading to the presence of a type-I multiferroic phase with huge electric polarization. On further cooling to 48 K, a type-II multiferroic phase induced by the special spin structure composed of both Mn- and Cr-sublattices emerges, accompanied by considerable magnetoelectric coupling. BiMn Cr O thus provides a rare example of joint multiferroicity, where two different types of multiferroic phases develop subsequently so that both large polarization and significant magnetoelectric effect are achieved in a single-phase multiferroic material.

Suffering from sluggish charge transfer kinetics, carbon‐based perovskite solar cells (C‐PSCs) lag far behind the Ag/Au‐based normal PSCs in power conversion efficiency (PCE). Herein, the use of defective multi‐walled CNT (D‐MWCNT) is demonstrated to tune the charge transfer kinetics regarding hole transport layer (HTL) and the interface between HTL and carbon electrode. Benefiting from the electrostatic dipole moment interaction between the terminal oxygen‐containing groups of D‐MWCNT and 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene, an interface coupling at molecular level is established and in turn, allows rapid charge transfer by edge effect induced electron redistribution and 1D hyper‐channels. Meanwhile, a seamless connection between HTL and carbon electrode is achieved in a novel modular C‐PSCs due to D‐MWCNT induced interface coupling with graphene at nanometer scale. Based on this strategy, high PCEs up to 22.07% (with a certified record PCE of 21.9% to date for C‐PSCs) and excellent operational stability have been achieved.

The magnetoelectric multiferroicity is not expected to occur in a cubic perovskite system due to the high structural symmetry. By versatile measurements in magnetization, dielectric constant, electric polarization, neutron and X-ray diffraction, Raman scattering as well as theoretical calculations, we reveal that the A-site ordered perovskite LaMn 3 Cr 4 O 12 with cubic symmetry is a novel spin-driven multiferroic system with strong magnetoelectric coupling effects. When magnetic field is applied in parallel/perpendicular to electric field, the ferroelectric polarization can be enhanced/suppressed significantly. The unique multiferroic phenomenon observed in this cubic perovskite cannot be understood by conventional spin-driven microscopic mechanisms. Instead, a nontrivial effect involving the interactions between two magnetic sublattices is likely to play a crucial role. 3The magnetoelectric (ME) multiferroicity with coupled ferroelectric and magnetic orders have received much attention due to their great potential for numerous applications [1][2][3][4][5][6][7][8]. Perovskite is one of the most important material systems for multiferroic study. Since the discovery of multiferroic behaviors in perovskite BiFeO 3 and TbMnO 3 [2,3], a large number of multiferroic materials with different physical mechanisms have been found in the last decade [9][10][11][12][13]. Among them, the spin-induced multiferroics have received the most attention because the ferroelectricity is induced by magnetic structures so that a strong ME coupling would be expected [14][15][16]. Several theories such as spin-current model (or inverse Dzyaloshinskii-Moriya interaction), exchange striction mechanism and d-p hybridization mechanism have been proposed to account for the spin-induced ferroelectricity in ME multiferroics by special spin textures such as non-collinear spiral spin structures and collinear E-type antiferromagnetic (AFM) structure with zigzag spin chains [17][18][19][20][21]. It is well known that a cubic perovskite lattice is unfavorable for ferroelectricity due to the existence of an inversion center. However, the total symmetry for an ME multiferroics is the product of the crystal and magnetic symmetries. Therefore, in principle, it is possible to find an ME multiferroics in a cubic perovskite system if its magnetic structure breaks the space inversion symmetry. Nevertheless, such an intriguing case has never been found in previous studies. 4The A-site ordered perovskite with a chemical formula of AA′ 3 B 4 O 12 provides an opportunity for searching ME multiferroics in a cubic lattice.This type of ordered perovskite can be formed when three quarters of the A-site of a simple ABO 3 perovskite is substituted by a transition-metal ion A′ (Fig. 1a) [22]. Since both A′ and B sites accommodate magnetic transition-metal ions, multiple magnetic interactions may develop while the crystal structure can be finely tuned by selecting appropriate A′ and B elements to maintain a cubic lattice [23][24][25][26][27]. In this lette...

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Manganese(II)-doped perovskite nanocrystals (NCs), because of their unique dual-color (from host excitons and Mn-dopants) emission property, are promising materials for various optical applications. Because the excited state at Mn 2+ is extremely long-lived, one or more host excitons coexisting with an excited Mn 2+ can be generated in the same NC under continuous excitation, and the behavior of exciton in the presence of excited Mn 2+ can determine the optical property of Mn-doped NCs. Herein, by using pump−pump−probe transient absorption spectroscopy, we show that, in Mn-doped CsPbCl 3 NCs, the host exciton can undergo ultrafast nonradiative Auger-like recombination (τ Aug ≈ 12 ps) when coexisting with the excited state at Mn 2+ . Such fast Auger-like process competes with the exciton-to-dopant energy transfer (τ IET ≈ 303 ps) and, thus, allows the Mn-dopant emission from only one Mn 2+ site per NC at a time. This dopant-induced Auger-like recombination should correspond to the broadly observed excitation-dependent saturation of dopant emission in Mn-doped NCs, and also makes the Mn-doped NC a potential single photon emitter.