Atomic Level Insights into Metal Halide Perovskite Materials by Scanning Tunneling Microscopy and Spectroscopy

Abstract

directions.I nset:C orresponding I(V)spectrum. b) Comparison of density of states calculations on two different domains:polar (solid line) and nonpolar (dotted line). Inset:E nlargement of the energy region close to the Fermi level. c) dI/dV spectra of cubic MAPbBr 3 .The black line was obtained in the dark and the orange line obtained under irradiation with light. Panels (a-c) are reprinted from Ref. [18e] with permission. Copyright 2015 AmericanC hemical Society.d )UPS and IPES spectra of MAPbBr 3 with DFT simulations. Reprinted from Ref. [44] with permission.

Superexchange-induced Pt-O-Ti 3+ site on single photocatalyst for efficient H 2 production with organics degradation in wastewater

“…1 D , Inset ) ( 28 ). Note that the atomic number is positively correlated with the brightness of atoms in HAADF-STEM, with Pt (78) atoms being brighter than Ti ( 22 ) atoms. Therefore, the local atomic structure of Pt in BTPO v can be determined.…”

“…Construction of synergistic active sites with short charge migration paths in a single catalyst enables the targeted accumulation of electrons and holes, which facilitates the simultaneous oxidation and reduction reactions in one system ( 10 , 12 ). Perovskite oxides with ABO 3 structure have been reported for various applications, where A and B refer to cations from the rare-earth/alkaline-earth group and transition metal group, respectively ( 21 , 22 ). Benefiting from the multiple atoms and variable structures, physical correlation effects (Jahn–Teller effect, superexchange effect and so on) are rich in perovskite oxides, providing a distinctive modulation method for the separation and directed transport of photoinduced charges ( 23 ).…”

Formation of Dual Bands in Mixed-Halide Perovskites During Photoinduced Halide Segregation

“…In Figure a, we present a typical d I /d V spectrum of the mixed-halide perovskite in its ultrathin form under dark conditions. Since a d I /d V spectrum has a correspondence to the DOS of the material, we could derive the CB and VB edges of the material at the point of investigation. , With the voltage being applied to the sample surface, the first peak in the positive bias region of a d I /d V spectrum signifies the injection of electrons from the tip to the sample and consequently provides the location of the CB of the sample; likewise, the first peak in the negative bias region signifies the withdrawal of electrons from the semiconductor and consequently refers to the VB. , With STS being an extremely localized mode of measurement, we thereby recorded spectra at many different points on the ultrathin film. The CB and VB energies were derived from each spectrum and collated to draw their histograms (Figure b).…”

Pathways of Water-Induced Lead-Halide Perovskite Surface Degradation: Insights from In Situ Atomic-Scale Analysis

“…Both methods provide effectively identical surface conditions . Since 2015, the atomic structures of pristine perovskite surfaces and defect structure and dynamics have been extensively investigated using scanning tunneling microscopy (STM) in conjunction with density functional theory (DFT) calculations, which have provided a fundamental understanding of the correlation between the surface structures and the optoelectronic properties of OHPs. − However, the STM measurements reported up to the present were obtained under UHV conditions and at low temperature, i.e., liquid nitrogen or helium temperature, or at ultralow water vapor exposure . In our previous reports, utilizing contact-mode atomic force microscopy (AFM) measurements together with DFT calculations, we showed that UHV-cleaved pristine MAPbBr 3 surfaces exhibit two surface domains, namely MA–Br and Pb–Br terminated surfaces (see Figure S1), and the degradation pathways in UHV conditions. , We reported that, in UHV chambers, the residual water of the partial pressure of 8 × 10 –10 Torr induced a slow degradation of MAPbBr 3 surfaces, over a time scale of weeks, leading to the formation of PbBr 2 clusters.…”