Effect of Mn²⁺ ions and TOP molecules on the luminescence properties of oleic acid caped CsPbI₃ nanocrystals

Abstract Due to the easy transformation to the non-luminous yellow δ-CsPbI₃ phase in air, α-CsPbI₃ nanocrystalline materials with red light emission find limited applications. Lifting its structural stability is a challenge in its quantum dot (QD) lighting field. Here we studied the doping of Mn²⁺ ions (5.0%) and processing by a small amount (0.315 ml) of TOP molecules on the OA-capped CsPbI₃ nanocrystals. It is found that after the successful introduction of Mn²⁺ into the CsPbI₃ nanocrystal, the grain size reduces, which leads to a stronger quantum confinement effect than the undoped QDs, which leads to the blue shift of PL and absorption spectra. The incorporation of Mn²⁺ simultaneously reduced defects and lifted the luminescence efficiency and lifetimes of QDs, the cause for the above optical behavior is due to the formation of excitonic magnetic polaron (EMP) excitons near the bandedge. On the other hand, the treated TOP molecule on the OA-capped NCs did not significantly affect their room-temperature luminescence. However, it improved the low-temperature emission performances of QDs significantly. Moreover, the TOP-treated QDs fixed in the PMMA film can transform into rod-like shapes in acidic environments, giving strong stability for emission, especially for the Mn-doped CsPbI₃ QDs. This work has been done to improve the stability and emission efficiency of related QDs through the EMP formation near band-edge and surface modification of CsPbI₃ NCs, favoring their potential applications in display and low-temperature light-emitting devices.