New perovskite material for lead-free solar cells

Researchers from the Amar Thlidji University in Algeria have conducted a theoretical study to investigate if a perovskite material known as KGeCl₃ may be used for applications in photovoltaics.

“KGeCl3 is one of the compounds that can be produced in the laboratory and has not been discovered in nature until now,” the research's corresponding author, Mohammed ElSaid Sarhani, told pv magazine.

In the study “AB-INITIO study of electronic, mechanical, optical and thermoelectric properties of KGeCl₃ for photovoltaic application,” published in Heliyon, Sarhani and his colleagues used the WIEN2k software to analyze the electronic, elastic, optical, and thermoelectric characteristics of the KGeCl₃ perovskite across its cubic, tetragonal, and orthorhombic phases.

The software allows users to perform electronic structure calculations of solids using density functional theory (DFT), which is a quantum-mechanical atomistic simulation approach to analyze a wide variety of properties of almost any kind of atomic system, including molecules, crystals, surfaces, and electronic devices.

“DFT is particularly well-suited for large systems, making it valuable for studying complex molecules,” the scientists stressed, noting that they also used the Boltzmann transport theory to assess the thermoelectric properties of the perovskite material. The Boltzmann approach enables the description of electron transport in materials with a complex band structure.

Through their analysis, the academics found that the KGeCl₃ perovskite has stable structures in all three configurations and “good” elastic properties.

“According to the electronic band structure calculation, KGeCl₃ perovskite is a direct bandgap semiconductor with bandgap energies of 0.92 eV, 1.26 eV, and 1.88 eV for cubic, tetragonal, and orthorhombic phases, respectively,” they also stated. “This implies that the material could be used in optoelectronic applications including photovoltaic devices.”

Sarhani also explained that the novel material is not the cheapest, as it contains germanium. “But the cost of producing this type of material is cheaper than other materials, thanks to the ease and conditions of its manufacture,” he emphasized. “It does not require high pressures or a high degree of purity. In addition, its production protocol is easy and simple.”

The scientists concluded by saying that KGeCl₃ perovskite may be used for lead-based perovskite materials in solar cells and other optoelectronic devices. “Overall, our study demonstrates the potential of KGeCl₃ perovskite as a multifunctional material with promising structural, electronic, optic, and thermoelectric properties across different crystal structures,” they said.