Tweaking the band gap and photoluminescence of CsPbI3 perovskite by Mn alloying

Alloying semiconductor nanocrystals with impurity can stabilize their phase with modulation of their morphology, lattice structure, photophysical and electronic properties which enhance their suitability towards solar cells and light-emitting diodes (LEDs). Herein we sought to substitute Mn²⁺ in CsPbI₃ nanoparticles (NPs) to overcome the phase transformation issue as well as to tune the electronic and optical properties of this perovskite material. The phase of the alloyed CsPbI₃ NPs was stabilized endowing high crystalline quality which can be clearly seen in X-ray diffraction (XRD). XRD plot depicts that impurity peaks arise in the case of CsPbI₃ NPs while the phase of Mn²⁺ alloyed NPs was stabilized upto 1 month. The decrease in lattice parameter values from 6.019 Å to 5.987 Å has been observed for pure CsPbI₃ and alloyed CsPbI₃ NPs respectively attributed to the reduction of the size of the cubic phase crystal structure due to the introduction of small size Mn²⁺ in place of large-sized Pb²⁺. The decrement in the lattice parameter further confirms the alloying of CsPbI₃ NPs with Mn²⁺. The absorption and emission peaks were tweaked in the synthesized CsPbI3 NPs after alloying which can be observed from the absorption spectrum and photoluminescence (PL). Alloying of CsPbI₃ NPs with Mn²⁺ leads to shifting in bandgap from 1.70 eV to 1.79 eV, PL peak from 671 nm to 654 nm, and absorption spectrum from 645 nm to 637 nm which suggest the tailoring of its novel properties. This investigation suggests the suitability of Mn²⁺ alloyed CsPbI₃ NPs in the area of optoelectronics.