Lead-free halide perovskites for optoelectronic application: investigation of morphological, optical and electrical conductivity

Being a research hotspot for the last decade, hybrid perovskites are now showing their romise in numerous optoelectronic devices. In this paper, the perovskite (CH3NH3)(3)Bi2Cl9 compound was successfully synthesized via the slow solvent evaporation method. The results of the analysis of X-ray diffraction suggest that the sample under investigation exhibits orthorhombic crystalline structure, characterized by the Pnma space group. The calculated and observed patterns exhibited good agreement after Rietveld refinement. SEM analysis showed that the average grain size of the sample is approximately 9 mu m. The semiconductor nature and the photodetectors application are confirmed by an optical absorption measurement, which has an indirect band gap of about 3 eV. Cole-Cole plot of the complex impedance was examined over a wide temperature and frequency range. Reduction in real part Z' was observed as a function of temperature and frequency, which indicates an increase in ac conductivity, and negative temperature coefficient of resistance (NTCR). The frequency-dependent ac conductivity data are modeled using power law response to resolve various types of charge species and conduction mechanism present in the studied compound. The temperature dependent ac conductivity study suggests thermally activated electrical process which is modeled using Arrhenius equation and activation energies is estimated.