Dielectric study and optical properties of the two-dimensional perovskite (CH₃NH₃)₂Sn(SCN)₂ Cl₂ for optoelectronic applications

In recent years, hybrid halide and pseudohalide perovskites have been developed as a class of efficient photovoltaic absorbers with excellent electronic properties. Layered perovskite (CH₃NH₃)₂ Sn(SCN)₂Cl₂ was recently identified as a promising PV candidate due to its increased stability and favorable electronic properties. Here, we demonstrate the optical and dielectric properties of 2D hybrid perovskites. The dielectric and ferroelectric properties were investigated in the frequency range from 20 to 2 MHz and the temperature range from 300 to 385 K. The temperature dependence of the dielectric constant at different frequencies leads to a diffusion peak, which is attributed to the appearance of the relaxed ferroelectric behavior in (CH₃NH₃)₂ Sn(SCN)₂Cl₂ . Complex impedance and modulus spectra unambiguously demonstrate the contribution of grain and grain boundary effects to the conduction properties of (CH₃NH₃)₂ Sn(SCN)₂Cl₂ . The equivalent circuit model [(R_gQ_g) (R_gbQ_gb)] is used to account for the electrical parameters associated with the different phases (grains and grain boundaries) with different relaxation times. The optical band gap of (CH₃NH₃)₂Sn(SCN)₂Cl₂ determined by UV-Vis spectroscopy reveals a band gap of 1.70 eV. These results suggest the possibility that (CH₃NH₃)₂Sn(SCN)₂Cl₂ analogs have properties suitable for photovoltaic top cells in tandem devices. (author)