Abstract
Report on systematic theoretical investigations of the effect of a mixed tin-lead cation strategy on structural, electronic and optical properties of orthorhombic methylammonium lead bromide perovskite using state-of-the-art first-principles calculation based on the hybrid density functional theory method. Our findings reveal that the band gap value of the alloy can be progressively tuned from pristine MAPbBr(3) to MASnBr(3), showing a quasi-linearly with the Sn concentration. Therefore, the band gap value is reduced from 2.7 eV to 1.58 eV when 75% amounts of Sn are incorporated into perovskite lattice. The improved absorption peaks toward visible region are observed owing to the increased composition of Sn substitutional at Pb in perovskite structures. Moreover, the solar cell performance parameters are also investigated using numerical device simulation. Our simulations show that the efficiencies of mixed Sn-Pb perovskite -based devices are significantly enhanced up to 11% compared with those based on pristine MAPbBr(3). This result highlights MAPb(0.25)Sn(0.75)Br(3) as a promising less toxic absorber for solar cell devices with the greatest simulated efficiency of 23.2%. Our findings suggest that a cation mixing scheme can be explored to tune the stability, band gap, and device performance of perovskite-based materials, which can be notably effective for designing high-efficiency performance of Sn-Pb-based mixed bromide perovskite solar cells.