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 time an all HTL-free non-toxic perovskite solar tandem device using SCAPS-1D. The (MAGeI3) with 1.9eV band gap is employed as a top-cell, while, the bottom-cell is FASnI3 with a band gap of 1.41eV. this new study is interesting since we remov 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, the ETL thickness, the ETL electron affinities, and the capture cross-section , and the effect of various ETL on the device performance of bottom sub-cell. Then, The tandem solar cell is then constructed using these individually HTL-free optimized sub-cells. A current matching J SC of 15.85/cm 2 was produced between the top and bottom sub-cell thickness of 860nm and 925nm, respectively. The tandem device simulation with MAGeI3 on FASnI3 yielding a PCE of 25.69%, V oc =1.3681V; J sc = 15.85mA/cm 2 , and FF= 75.95%, that 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 devices.