HTL-free non-toxic perovskite tandem solar device MAGeI3/FASnI3 with 25.69% efficiency: design and simulation using SCAPS

Lead-free hybrid organic–inorganic perovskite have gained remarkable interest for photovoltaic application due to their lack of toxicity. In this work, we design and simulate for the first all HTL-free non-toxic perovskite tandem solar device using SCAPS-1D. The (MAGeI3) with 1.9 eV band gap is employed as a top cell, while the bottom cell is FASnI3 with a band gap of 1.41 eV. The proposed tandem device is interesting since we remove the HTL layer from two sub-cells. Initially, individual sub-cell improvement was carried out through varying the solar cell’s parameters, starting with the absorber thickness and doping level, ETL thickness and electron affinities of both sub-cells. The effects of capture cross section of ETL/absorber interface as well as various ETL on the performance of bottom sub-cell have been studied. The efficiency of the devices has been demonstrated to be affected by all these parameters. Then, the tandem solar cell is constructed using these individual HTL-free optimized sub-cells. A current matching J_SC of 15.85/cm² was produced between the top and bottom sub-cell thickness of 860 and 925 nm, respectively. The tandem device simulation with MAGeI3 on FASnI3 yielding a PCE of 25.69%, V_OC = 1.3681 V; J_SC = 15.85 mA/cm², and FF = 75.95% was much greater than each sub-cells output. The findings of this study demonstrate the possibility of using cheap, HTL-free non-toxic perovskite solar cells to produce high PCE in tandem solar devices.