Exploring Optoelectronic Behavior and Solar Cell Efficiency of Double Halide Perovskites M₂KIrCl₆ (M = Cs, Rb)...

Due to environmental concerns with lead-based perovskite solar cells (PSCs), attention has shifted toward safer alternatives like M₂KIrCl₆ (M = Cs, Rb). This study extensively investigates the structural, electronic, and optical properties of M₂KIrCl₆ using density functional theory (DFT). The analysis evaluates the suitability of these compounds as absorber materials in solar cells, emphasizing their environmental friendliness, stability, and efficiency for light-harvesting applications. The structural stability of M₂KIrCl₆ double halide perovskites is analyzed using tolerance factors (τ₁, μ, τ₂), with dynamical stability confirmed via phonon dispersion analysis. Negative formation energy (E_f) and binding energy (E_b) further corroborate their thermodynamic stability. The direct band gaps calculated using both GGA-PBE and TB-mBJ methods were found to be 1.08 and 1.99 eV for Cs₂KIrCl₆, and 1.12 and 2.10 eV for Rb₂KIrCl₆, respectively. These bandgap values fall within the optimal range (0.8-2.2 eV) necessary for efficient photovoltaic conversion, showcasing their capability to serve as absorber layers in photovoltaic devices. Furthermore, these compounds demonstrate exceptional optical properties, including high absorption coefficients (∼10⁴ cm^-1), low energy losses, and minimal reflectivity (<15%), emphasizing their suitability for advanced optoelectronic and photovoltaic applications. To optimize solar cell performance, SCAPS-1D software was utilized to investigate various device configurations incorporating different Hole Transport Layers (HTLs) and Electron Transport Layers (ETLs). Among 32 configurations tested, the ITO/ZnO/Cs₂KIrCl₆/V₂O₅ structure reached a peak power conversion efficiency (PCE) of around 21.30%, while the ITO/ZnO/Rb₂KIrCl₆/V₂O₅ configuration exhibited around 18.30%. Additionally, the impact of ETL and absorber layer thicknesses, series and shunt resistances, and operating temperatures on device performance was thoroughly explored. Crucial photovoltaic metrics, including current density-voltage (J-V) curves, capacitance, quantum efficiency, Mott-Schottky characteristics, and photocarrier generation-recombination rates, were comprehensively analyzed, underscoring the remarkable potential of M₂KIrCl₆ as efficient and cost-effective materials for future solar energy and optoelectronic applications.