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. 2023 Jun 13;13(26):17750-17764.
doi: 10.1039/d3ra02731g. eCollection 2023 Jun 9.

Lead-free double perovskite Cs2MBiCl6 (M = Ag, Cu): insights into the optical, dielectric, and charge transfer properties

Mohamed Ben Bechir  1 , Mohamed Houcine Dhaou  2
Affiliations

Lead-free double perovskite Cs2MBiCl6 (M = Ag, Cu): insights into the optical, dielectric, and charge transfer properties

Mohamed Ben Bechir et al. RSC Adv. .

Abstract

Recently, double perovskites have shown excellent potential considering the instability and toxicity problems of lead halide perovskites in optoelectronic devices. Here, the double perovskites Cs2MBiCl6 (M = Ag, Cu) were successfully synthesized via the slow evaporation solution growth technique. The cubic phase of these double perovskite materials was verified through the X-ray diffraction pattern. The investigation of Cs2CuBiCl6 and Cs2AgBiCl6 utilizing optical analysis showed that their respective indirect band-gap values were 1.31 and 2.92 eV, respectively. These materials, which are double perovskites, were examined using the impedance spectroscopy technique within the 10-1 to 106 Hz frequency and 300-400 K temperature ranges. Jonncher's power law was utilized to describe AC conductivity. The outcomes of the study on charge transportation in Cs2MBiCl6 (where M = Ag, Cu) suggest that the non-overlapping small polaron tunneling mechanism was present in Cs2CuBiCl6, whereas the overlapping large polaron tunneling mechanism was present in Cs2AgBiCl6.

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Conflict of interest statement

There are no conflicts to declare.

Figures

Fig. 1
Fig. 1. (a) Powder X-ray diffractogram of Cs2MBiCl6 (M = Cu, Ag) at room temperature in the 2θ range 10–50°. (b) Constructed cubic crystal structure of Cs2MBiCl6 (M = Cu, Ag). (c) TG data of Cs2MBiCl6 (M = Cu, Ag) in the temperature range of 100–1190 K.
Fig. 2
Fig. 2. Absorption spectra of (a) Cs2CuBiCl6 and (b) Cs2AgBiCl6. The inset shows the Tauc plot.
Fig. 3
Fig. 3. Curves of ln(αhν) vs. ln(hν − Eg) for (a) Cs2CuBiCl6 and (b) Cs2AgBiCl6.
Fig. 4
Fig. 4. Frequency dependence of Z′(ω) for (a) Cs2CuBiCl6 and (b) Cs2AgBiCl6 at various temperatures.
Fig. 5
Fig. 5. Frequency dependence of Z′′(ω) for (a) Cs2CuBiCl6 and (b) Cs2AgBiCl6 at various temperatures.
Fig. 6
Fig. 6. Fitted Cole–Cole plots of (a) Cs2CuBiCl6 and (b) Cs2AgBiCl6 at different temperature, (the equivalent circuits have shown in inset). (c) Representation of grain and grain boundary within material. (d) The variation of Cgb of Cs2MBiCl6 (M = Cu, Ag) at different temperatures.
Fig. 7
Fig. 7. Variation of ε′(ω) of (a) Cs2CuBiCl6 and (b) Cs2AgBiCl6 at different temperatures. Variation of ε′′(ω) of (c) Cs2CuBiCl6 and (d) Cs2AgBiCl6 at various temperatures. Frequency-dependent dielectric loss (tan δ) of (e) Cs2CuBiCl6 and (f) Cs2AgBiCl6.
Fig. 8
Fig. 8. Variation of M′(ω) of (a) Cs2CuBiCl6 and (b) Cs2AgBiCl6 at different temperatures. Variation of M′′(ω) of (c) Cs2CuBiCl6 and (d) Cs2AgBiCl6 at various temperatures. (e) Arrhenius plots of Cs2MBiCl6 (M = Cu, Ag). Normalized imaginary modulus vs. f/fmax of (f) Cs2CuBiCl6 and (g) Cs2AgBiCl6 at various temperatures.
Fig. 9
Fig. 9. The variation of σac with frequency at different temperatures for (a) Cs2CuBiCl6 and (b) Cs2AgBiCl6. (c) Arrhenius plots of dc conductivity for Cs2MBiCl6 (M = Cu, Ag). (d) Temperature dependence of s and 1 − s for Cs2MBiCl6 (M = Cu, Ag).
Fig. 10
Fig. 10. (a) Temperature dependence of the ln(σAC) at different frequencies. (b) Frequency-dependent of the parameter Rω (Å) for Cs2MBiCl6 (M = Cu, Ag). (c) Frequency-dependent of the parameters α (Å−1), N(EF) (eV−1 cm−3).
Fig. 11
Fig. 11. (a) Nyquist diagram and (b) AC conductivity of Cs2MBiCl6 (M = Cu, Ag) at 340 K.
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