Highly Efficient (>36%) Lead-Free Cs2BiAgI6/CIGS Based Double Perovskite Solar Cell (DPSC) With Dual-Graded Light Absorber Layers for Next Generation Photovoltaic (PV) Technologies

Perovskite solar cells (PSCs) are a novel emerging technology that are the third generation of solar cells, following wafer-based and thin-film-based predecessors. Solar photovoltaic (PV) technology that uses perovskite materials has a significant advantage over conventional solar PV, as it can respond to various light wavelengths and increase the amount of sunlight converted to electricity. In addition, PSCs are flexible, semi-transparent, customizable, lightweight, and have a high power conversion efficiency (PCE). Through the use of dual-graded light absorber/active layers, and double perovskite lead-free material Cs
$_{2}$
BiAgI
$_{6}$
, this study seeks to increase the efficiency of PSCs. A unique device structure (ITO/ZnO/Double Perovskite Cs
$_{2}$
BiAgI
$_{6}$
/CIGS/High purity Spiro-OMeTAD/Au) of lead-free double perovskite material-based solar cell has been simulated using the SCAPS-1D one-dimensional solar cell capacitance simulator. The optimized solar cell output parameters achieved in this work include voltage in an open circuit (Voc) of 1.2258 V, current density in a short circuit (Jsc) of 34.292 mA/cm
$^{2}$
, fill factor (FF) of 85.95
$\%$
, and power conversion efficiency (PCE) of 36.13
$\%$
, which gets close to the single-junction PSCs' Shockley-Queisser Efficiency (SQ) limit.