Perovskites are among the most promising candidates for improving the efficiency of solar cells. Layered perovskites with weak van der Waals interlayer interactions can be exfoliated down into monolayers through mechanical methods. Herein, we investigate recently synthesized all-inorganic perovskite, Cs₂XI₂Cl₂ (X = Pb, Sn), in bulk and monolayer limit using ab-initio calculations. The transition from bulk to monolayers negligibly widens the bandgaps but does not change their type and location, which indicates the robust electronic properties of the compounds. Moreover, the spin-orbit (SO) interaction reduces the bandgap, especially in Pb-based monolayers. Besides, the behavior of these systems is dependent on the type, value, and direction of the induced strains. We predict that the monolayer perovskite can sustain uniaxial strain in the range of −10% to +16% and biaxial strain up to $\pm$ ~10%. Additionally, a direct-indirect transition is predicted for biaxial strains higher than 1%. The variation of the bandgaps with the strain behaves as a non-linear and nearly oscillatory curve. Furthermore, a semiconductor-to-metal transition occurs at the biaxial strain of −10%. More interestingly, the optical absorption coefficient is improved in the presence of strain. The hole and electron mobility of Cs₂PbI₂Cl₂ monolayer is obtained as 880 and 2360 cm²/V, respectively which are favorable for electronic devices. In addition, the strain can adjust the photocatalytic ability of the monolayer perovskite for water splitting. Our results promise a high potential of Cs₂XI₂Cl₂ (X = Pb, Sn) perovskites for photovoltaic, optoelectronic, and mechatronic systems.

钙钛矿是提高太阳能电池效率的最有希望的候选者之一。具有弱范德华层间相互作用的层状钙钛矿可以通过机械方法剥离成单层。在这里，我们研究最近合成的全无机钙钛矿，Cs ₂ XI ₂ Cl ₂（X = Pb，Sn），使用ab-initio计算得出整体和单层极限。从体层到单层的过渡几乎可以忽略不计，但不能改变带隙，但不会改变其类型和位置，这表明该化合物具有强大的电子性能。此外，自旋轨道（SO）相互作用减小了带隙，尤其是在基于Pb的单层中。此外，这些系统的行为还取决于诱导应变的类型，值和方向。我们预测，单层钙钛矿可以承受-10％至+ 16％的单轴应变，而双轴应变高达$\pm$〜10％。另外，对于高于1％的双轴应变，预计将发生直接-间接转变。带隙随应变的变化表现为非线性且接近振荡的曲线。此外，半导体到金属的转变发生在-10％的双轴应变下。更有趣的是，在应变的存在下光吸收系数得到改善。Cs ₂ PbI ₂ Cl ₂单层的空穴迁移率和电子迁移率分别为880和2360cm ² / V，这对于电子器件是有利的。另外，该菌株可以调节钙钛矿单层对水分解的光催化能力。我们的结果表明，Cs ₂ XI ₂ Cl具有很高的潜力_2个（X = Pb，Sn）钙钛矿，用于光伏，光电和机电系统。