Slow Electron–Hole Recombination in Lead Iodide Perovskites Does Not Require a Molecular Dipole

Abstract

Hybrid organic/inorganic lead iodide perovskites of the formula APbI3, where A is a molecular cation such as methylammonium, exhibit remarkably slow photoinduced charge carrier recombination rates, for reasons that remain uncertain. Prevalent hypotheses credit this behavior to the unique dipolar nature of the molecular cation. Herein, transient terahertz spectroscopy is applied to solution-processed, all-inorganic, perovskite-phase cesium lead iodide (CsPbI3) thin films, which lack such a dipole. The recombination kinetics are studied as a function of the initial photoinduced carrier concentration and the wavelength of excitation. A kinetic model combining diffusion and recombination is fit to the data, from which the rate constants are determined, revealing a bimolecular recombination rate of 10–10 cm3 s–1, comparable to high-quality, single-crystal, direct-gap semiconductors. This rate, as well as a charge carrier mobility > 30 cm2 V–1 s–1 measured herein for CsPbI3, are similar to values reported for the hybrid perovskites, strongly suggesting that the organic cation does not confer a fundamental advantage.

Synergy of Hydrophobic Surface Capping and Lattice Contraction for Stable and High‐Efficiency Inorganic CsPbI2Br Perovskite Solar Cells

“…However, their poor stability has been a challenging problem, mainly due to the inherent instability of their organic components . Gratifyingly, by replacing the organic cation with Cs + , their compositional stability is greatly improved …”

Metal halide perovskite nanocrystals and their applications in optoelectronic devices

“…For example, under environmental stress, MAPbI 3 dissociates into PbI 2 and CH 3 NH 3 I, and CH 3 NH 3 I is volatile. All‐inorganic perovskites do not produce volatile decomposition at relatively high temperature, which is more stable under various stresses . For CsPbBr 3 and CsPbCl 3 , they have large band gaps and cannot produce a wide range of optical absorption, which is not very appropriate for solar cells.…”

“…All-inorganic perovskites do not produce volatile decomposition at relatively high temperature, which is more stable under various stresses. 223,224 For CsPbBr 3 and CsPbCl 3 , they have large band gaps and cannot produce a wide range of optical absorption, which is not very appropriate for solar cells. The all-inorganic lead-halide perovskite with the most suitable bandgap E g for photovoltaic applications is cubic (α) phase CsPbI 3 (E g = 1.73 eV).…”

Anorganische CsPbX3‐Perowskit‐Solarzellen: Fortschritte und Perspektiven

“…Es scheint, dass die Mobilitätswerte fürC sPb-HaPs denen der entsprechenden Hybrid-HaPs ähnlich sind. [50] Für CsPbBr 3 wurden Lebensdauern von 2-7 msf ürm akroskopische Einkristalle gemessen. 25 cm 2 V À1 s À 1f ürC sPbI 3 , [49,50] etwas kleinere Werte (ca.…”

“…25 cm 2 V À1 s À 1f ürC sPbI 3 , [49,50] etwas kleinere Werte (ca. 1 mm [50] geschätzt, während füre inkristallines CsPbBr 3 L d -Werte fürE lektronen und Lçcher von ca. Diese Werte sind vergleichbar mit den typischen Werten fürhybride Cs-HaPs.Die Ladungsträgerlebensdauern sind variabler, was nicht überraschend ist.…”