Excellent Long‐Range Charge‐Carrier Mobility in 2D Perovskites

Abstract

The use of layered, 2D perovskites can improve the stability of metal halide perovskite thin films and devices. However, the charge carrier transport properties in layered perovskites are still not fully understood. Here, the sum of the electron and hole mobilities (Σμ) in thin films of the 2D perovskite PEA2PbI4, through transient electronically contacted nanosecond‐to‐millisecond photoconductivity measurements, which are sensitive to long‐time, long‐range (micrometer length scale) transport processes is investigated. After careful analysis, accounting for both early‐time recombination and the evolution of the exciton‐to‐free‐carrier population, a long‐range mobility of 8.0 +/− 0.6 cm2 (V s)–1, which is ten times greater than the long‐range mobility of a comparable 3D material FA0.9Cs0.1PbI3 is determined. These values are compared to ultra‐fast transient time‐resolved THz photoconductivity measurements, which are sensitive to early‐time, shorter‐range (tens of nm length scale) mobilities. Mobilities of 8 and 45 cm2 (V s)–1 in the case of the PEA2PbI4 and FA0.9Cs0.1PbI3, respectively, are obtained. This previously unreported concurrence between the long‐range and short‐range mobility in a 2D material indicates that the polycrystalline thin films already have single‐crystal‐like qualities. Hence, their fundamental charge carrier transport properties should aid device performance.

How to GIWAXS: Grazing Incidence Wide Angle X‐Ray Scattering Applied to Metal Halide Perovskite Thin Films

“…By tracking the motions of over 600 GIWAXS diffraction spots, one can summarize the rotation and azimuthal behaviors of perovskite grains during pre-crystallization stage, as presented in Figure 36D. Notably, these apparent rotations of intermediate perovskite grains under thermal stress can be mainly [216] Copyright 2016, Royal Society of Chemistry.…”

“…Notably, most of the changes are observed early on during annealing are linked to the evaporation of the solvent and sublimation of byproducts. Reproduced with permission [216]. Copyright 2016, Royal Society of Chemistry.…”

Carriers, Quasi-particles, and Collective Excitations in Halide Perovskites

“…Hence the PLQY only depends on the ratio of k 1 and k 1 exc . Figure b shows a simulation of the PLQY quasi‑2D when k 1 , k 2 , and k 3 are fixed but k 1 exc is varied. ,, In these quasi-2D HPs systems, the PLQY is much higher thanks to the efficient monomolecular radiative recombination. When n is larger, the high-order nonradiative Auger term ( k 3 n 2 ) starts to dominate, resulting in a drop in the PLQY similar to the case of 3D perovskites.…”

Tailoring the high-brightness “warm” white light emission of two-dimensional perovskite crystalsviaa pressure-inhibited nonradiative transition

“…Two-dimensional (2D) organic-inorganic hybrid perovskites have received tremendous attention for their diversity and stability compared to 3D perovskites. [1][2][3][4][5][6] Although a variety of 2D perovskites have been synthesized so far, further understanding the structure-property relationship of these 2D materials and improving their optical properties are essential for their practical applications. In particular, the development of white lightemitting perovskites always lags behind that of their green and red emission analogues, which limits their further application as single-component white light-emitting diodes (LEDs).…”