Structural stability, mechanical and optoelectronic properties of strain-tuned mixed-halide perovskites CsPbX3-aYa

Abstract

Lead-based all-inorganic metal halide perovskites are of current interest due to their novel properties and potential applications in optoelectronic devices. Controllably strain and mixed-halide compositions are valuable way of tuning the bandgap and improve optoelectronic properties. Here, structure stability, mechanical and optoelectronic properties of strain-tuned mixed-halide CsPbX3-aYa (X, Y =I, Br, Cl; a = 0, 1, 2, 3) are investigated by first-principles calculations. Results show that their structural stability were improved with the increasing of Br or Cl doping concentration. Elastic calculations indicates that these mixed-halide CsPbX3-aYa (X, Y =I, Br, Cl; a = 0, 1, 2, 3) compounds are all mechanically stable and possess superior ductility in the studied range of pressure, which makes them suitable for thin films and flexible solar cells. Moreover, the ductility becomes more excellent as the pressure increases. Electronic properties calculations exhibit that these compounds have similar band structure. That is, they are all direct bandgap semiconductors, and the energy gap decreases with increasing pressure, and finally all structures are transformed into metallic phase. Based on the electronic structure, the optical absorption coefficients are calculated, which show that the main absorption region shifts to red light and the absorption capacity enhancement with the increase of pressure, but decreases with the increase of doping concentration of Br or Cl doping.