Unveiling the Intrinsic Structure and Intragrain Defects of Organic–Inorganic Hybrid Perovskites by Ultralow Dose Transmission Electron Microscopy

Abstract

increased over the past decade. This is attributed to the intrinsically excellent photoelectric properties of photoactive perovskite materials, including tunable bandgap, high absorption coefficient, long carrier diffusion length, high photoluminescence quantum yield, and high color purity. [3][4][5] However, the long-term instability of PSCs [6] and PeLEDs [7] limits future commercialization. Device performance gradually degrades under external stimuli, such as moisture, oxygen, light, heat, and electric fields, [8] causing photocarrier recombination and ion migration [9] which are intimately linked to the device microstructure. [10,11] Perovskites are typically fabricated through techniques such as solution process [12][13][14] or thermal evaporation, [15] which can lead to local fluctuations in the microstructural features, such as the presence of grain boundaries, [16,17] intragrain defects, [18,19] surfaces, [20,21] and inhomogeneous domain structures. [22,23] These microstructures have a significant effect on recombination, carrier transport, band alignment, and electrical instability. [24] Transmission electron microscopy (TEM), combined with energy-dispersive X-ray spectroscopy (EDS), [25,26] electron energy loss spectroscopy (EELS), [16] cathodoluminescence (CL), [27] and photoluminescence [28] can provide direct and indispensable insights into the structure, composition, andThe ORCID identification number(s) for the author(s) of this article can be found under

Atomically Deciphering the Phase Segregation in Mixed Halide Perovskite

“…All (scanning) transmission electron microscopy ((S)TEM) analyses in this work were conducted under well-controlled imaging conditions avoiding irradiation damage (Table S1, Supporting Information). [29,30] Selected area electron diffraction (SAED) of an individual grain exhibits a typical orthorhombic phase CsPbIBr 2 , with space group Pnma (Glazer tilting a + b − b − , a = 8.21 Å, b = 8.26 Å, c = 11.76 Å), [31] observed along the [110] zone axis (Figure S1B,E, Figures S3A, Supporting Information). Indexing the SAED pattern reveals that it corresponds to two overlapping single-crystal domains of the orthorhombic CsPbIBr 2 (Figure S1E,F, Supporting Information).…”

Switchable coordination bonds in 3D cyano-bridged perovskite ferroelastics: achieving the largest leap of symmetry breaking and enhanced dielectric switching performance

“…[1][2][3][4][5][6][7][8] Organic-inorganic hybrid perovskites (OIHPs), in comparison with their inorganic counterparts, have garnered increasing interest in recent years due to their environmentally friendly nature, ease of processing, mechanical flexibility, affordability, and biocompatibility. [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] Their unique structures, where the inorganic component guarantees stability and fascinating electro-optical properties while the organic part provides structural flexibility and variability, offer great potential for constructing and optimizing multifunctional ferroelastic materials. [27][28][29][30][31][32][33][34] Among these, three-dimen-sional (3D) cyano-bridged perovskites have attracted considerable attention, primarily because many cyanide compounds exhibit an intriguing dielectric property switchability triggered by structural phase transitions.…”

Instability of Cs1-xFAxPbI3 quantum dots – the role of ion migration, octahedral tilt and the A-site cation

“…In the case of MAPbX3, intermediate phases were first detected from the appearance of additional (sometimes called 'forbidden') reflections in selected area diffraction (SAD) patterns (~1-2 e/Å 2 /s) 18,23,24,28 . Different structural models were proposed for these intermediate phases, such as ordered halogen vacancies 18,24,28 and octahedral tilt or rotation 23 , however, these models cannot be distinguished easily from SAD alone.…”

“…In the case of MAPbX3, intermediate phases were first detected from the appearance of additional (sometimes called 'forbidden') reflections in selected area diffraction (SAD) patterns (~1-2 e/Å 2 /s) 18,23,24,28 . Different structural models were proposed for these intermediate phases, such as ordered halogen vacancies 18,24,28 and octahedral tilt or rotation 23 , however, these models cannot be distinguished easily from SAD alone. Recently, further information was obtained for the specific case of MAPbI3 using low dose atomic resolution phase contrast TEM (HR-TEM) combined with a direct-detection electron counting camera (DDEC) which observed an intermediate phase of MA0.5PbI3 similar to that observed in FAPbI3 20 .…”