High dielectric performance with low losses in solution-grown CsPbBr3 single crystals revealed by impedance spectroscopy.

Abstract

In this study, the dielectric and electrical properties of a solution-grown CsPbBr3 single crystal were investigated in an Au/CsPbBr3/Au device configuration using broadband impedance spectroscopy (0.1 Hz-1 MHz, in the dark at room temperature). The fully inorganic CsPbBr3 single crystal was grown by the antisolvent vapor-assisted crystallization method, yielding a well-defined rectangular crystal with dimensions of approximately 5 × 5 × 2 mm. At high frequency the crystal combines a high apparent permittivity, ε' ≈ 110 at 1 MHz (planar-capacitor approximation, single crystal thickness), with low dielectric losses: the loss tangent decreases from tan δ ≈ 0.38 at 1 kHz to below 10-2 above ≈2 × 105 Hz and reaches ≈2 × 10-4 at 1 MHz (the upper end of the measured range). Toward low frequencies, ε' increases to ≈2400 at 0.1 Hz, reflecting the contribution of slow polarization processes and interfacial charge accumulation. Electric modulus analysis reveals a dominant relaxation maximum at f max ≈ 610 Hz, corresponding to a relaxation time of τ ≈ 2.61 × 10-4 s. Additional Havriliak-Negami-type fitting confirms the non-Debye character of the dielectric relaxation, with distributed relaxation contributions associated with ionic/space-charge polarization and charge-transport-related processes. Equivalent-circuit analysis using two serially connected R‖CPE branches (the series resistance was found to be negligible) provides a phenomenological separation of higher-frequency bulk-related and low-frequency interfacial contributions and yields an apparent resistivity of ρ ≈ 4.4 × 108 Ω cm. The results indicate a high apparent permittivity combined with low high-frequency losses in solution-grown all-inorganic CsPbBr3 single crystals and provide reference dielectric parameters for the modelling of perovskite-based devices; they were obtained on a single crystal in a two-terminal configuration, so the effects of crystal thickness and surface leakage remain to be investigated.

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