Investigation of the Mn dopant-enhanced photoluminescence performance of lead-free Cs2AgInCl6 double perovskite crystals

Abstract

The lead-free double perovskite Cs₂AgInCl₆ is a potential candidate for LEDs, the photoluminescence performance of which is reinforced greatly by Mn doping. Here, we analyzed the geometric, electronic and photoluminescence properties of Mn-doped Cs₂AgInCl₆ by means of first-principle calculations. We found that in the interior of Cs₂AgInCl₆, the Mn dopant formed defect complexes by substituting an Ag atom and generating an Ag vacancy (Mn_AgV_Ag) owing to the charge balance and the weak distortion of the metal octahedra. The Mn_AgV_Ag defect introduced two defect bands in the forbidden gap, which was contributed predominantly by the 3d orbitals of the Mn²⁺ ions. The electron transition of the Mn²⁺ ions from the first excited state to the ground state, i.e., from ⁴T₁ to ⁶A₁ states, gives rise to the PL spectrum that is lower than the bandgap. Therefore, we show that the Mn dopant indeed reinforces the PL performance of Cs₂AgInCl₆ greatly and is beneficial for its use as an LED material.