Extensive studies have demonstrated that all-inorganic lead-free halide perovskite solar cells as promising photoelectric devices are receiving great attention. In this paper, we have investigated the structures, electronical and optical properties of perovskite Cs₂Ti(Br_1-xY_x)₆ (Y = Cl, I, x = 0, 0.25, 0.5, 0.75, 1). When x = 0.25, the system Cs₂Ti(Br_0.75Cl_0.25)₆ has the suitable band gap value. With the increase of Cl content, the absorption coefficients showing blue shift which lead to the optical performance slightly decreased. But the systems become more stable. For the substitution of I to Br, the band gap values are lower than the optimal one. As to optical calculations, we find that the systems show obvious red shift, which result in the optical performance enhanced. However, the systems become unstable and not easy to be prepared. All calculations reveal that these excellent properties make Cs₂Ti(Br_0.75Cl_0.25)₆ as an ideal candidate material for perovskite solar cells.

广泛的研究表明，作为有前途的光电器件的全无机无铅卤化物钙钛矿太阳能电池受到了极大的关注。在本文中，我们研究了钙钛矿Cs ₂ Ti（Br _1-x Y _x）₆（Y = Cl，I，x = 0，0.25，0.5，0.75，1）的结构，电学和光学性质。当x = 0.25时，系统Cs ₂ Ti（Br _0.75 Cl _0.25）₆具有合适的带隙值。随着Cl含量的增加，显示出蓝移的吸收系数导致光学性能略有下降。但是系统变得更加稳定。对于将I替换为Br，带隙值低于最佳值。对于光学计算，我们发现系统显示出明显的红移，从而提高了光学性能。但是，系统变得不稳定并且不容易准备。所有计算表明，这些优异的性能使Cs ₂ Ti（Br _0.75 Cl _0.25）₆成为钙钛矿太阳能电池的理想候选材料。