An In-Depth Investigation of Lead-FreeKGeCl3Perovskite Solar Cells Employing Optoelectronic, Thermomechanical and Photovoltaic Properties: DFT and SCAPS-1D Frameworks

Abstract

Potassium Germanium Chloride (KGeCl3) emerges as a promising contender as an absorber material for lead-free perovskite solar cells (PSCs), offering significant potential and competitiveness in this domain. Nevertheless, KGeCl3-based PSCs are still striving to attain the exceptional performance levels demonstrated by hybrid PSCs. In this study, we conducted a density functional theory (DFT) investigation employing the Cambridge Serial Total Energy Package (CASTEP) code to analyze and assess the structural, electronic, mechanical, and optical characteristics of the cubic KGeCl3 absorber. The positive phonon dispersion curve confirms the dynamical stability of KGeCl3. The elastic constant satisfied the Born criteria, validating the mechanical stability and ductility of solid KGeCl3. The electronic band structure and density of states (DOS) affirmed that the KGeCl3 material is a semiconductor with a direct band gap of 0.754 eV. The study also identified key parameters of optical properties such as absorption, conductivity, reflectivity, dielectric function, refractive index, and loss function. These optical findings reveal the potential suitability of our compound KGeCl3 for solar applications. The Helmholtz free energy (F), internal energy (E), entropy (S), and specific heat capacity (Cv) are computed based on the phonon density of states. Additionally, we investigated twenty-four configurations comprising different combinations of electron transport layers (ETLs) and hole transport layers (HTLs) in SCAPS-1D software. For this purpose, ETLs such as Ws2, ZnSe, PCBM, C60 are utilized, while HTLs including CBTS, CdTe, CFTS, Cu2O, P3HT, PEDOT: PSS are employed. The highlighted structure, ITO/CBTS/ KGeCl3/Ws2/Ni, demonstrates remarkable performance with an efficiency of 22.01%, Voc of 0.6799 V, Jsc of 41.439 mA/cm2, FF of 78.12 %. To analyze Photovoltaic (PV) performance, we chose the top four solar cell (SC) configurations. Moreover, a comprehensive examination was conducted to assess the impact of various factors, including the thickness of different layers, capacitance, Mott-Schottky, series and shunt resistance, temperature, and generation-recombination rates, as well as J-V (current-voltage density) and quantum efficiency (QE) characteristics. These results are meticulously situated within existing research, demonstrating the study’s impact on non-toxic, inorganic perovskite solar technology.