Mg²⁺-Assisted Passivation of Defects in CsPbI₃ Perovskite Nanocrystals for High-Efficiency Photoluminescence

Abstract

CsPbI 3 perovskite nanocrystals (NCs) are emerging as promising materials for optoelectronic devices because of their superior optical properties. However, the poor stability of CsPbI 3 NCs has become a huge bottleneck for practical applications. Herein, we report an effective strategy of Mg 2+ -assisted passivation of surface defects to obtain high emission efficiency and stability in CsPbI 3 NCs. It is found that the introduced Mg 2+ ions are mainly distributed on the surface of NCs and then passivate the NC defects, enhancing radiative decay rate and reducing nonradiative decay rate. As a result, the as-prepared Mg 2+ -treated CsPbI 3 (Mg-CsPbI 3 ) NCs exhibit the highest photoluminescence quantum yield (PLQY) of 95%. The Mg-CsPbI 3 NC colloidal solution retains 80% of its original PLQY after 80 days of atmosphere exposure. The red perovskite light-emitting diodes based on the Mg-CsPbI 3 NCs demonstrate an external quantum efficiency of 8.4%, which shows an almost 4-fold improvement compared to the devices based on the untreated NCs.

H2O–NH4+-Induced Emission Modulation in Sb3+-Doped (NH4)2InCl5·H2O

“…Generally, this STE emission usually has a relatively long PL lifetime compared to the band edge free exciton emission (such as CsPbI 3 , the PL lifetime is on a nanosecond scale). 1 In these STE-emitting materials, the electron−phonon interaction is strong enough to elastically deform the lattice around the excited excitons. 34 This is the first interaction in this process.…”

“…In general, the transitions 1 P 1 → 1 S 0 and 3 P 1 → 1 S 0 are parity-allowed due to SOC, while transitions 3 P 0 → 1 S 0 and 3 P 2 → 1 S 0 are forbidden. , This microsecond scale PL lifetime is a typical feature of the triplet STE. Generally, this STE emission usually has a relatively long PL lifetime compared to the band edge free exciton emission (such as CsPbI 3 , the PL lifetime is on a nanosecond scale) . In these STE-emitting materials, the electron–phonon interaction is strong enough to elastically deform the lattice around the excited excitons .…”

“…In the past decade, apart from the significant progress in solar cells, lead-based metal halide perovskites have received widespread attention for their promising application prospects in the field of lighting and display due to their excellent optical properties. − However, the toxicity of lead hinders their further commercial application. For this reason, it is particularly important to explore and develop new lead-free and low-toxicity environmentally friendly perovskites or metal halides.…”

Phase-Stable and Highly Luminescent CsPbI3 Perovskite Nanocrystals with Suppressed Photoluminescence Blinking

“…Phase instability and deteriorating PL properties of these NCs arise from surface iodide vacancies, poor surface capping by the coordinating ligands, and the intrinsic disorder of the [PbI 6 ] 4– units. ,, The nature of the surface of the NCs depends largely on their method of preparation. ,− The widely used two-precursor method, in which PbI 2 is used as a precursor for both lead and halide, yields NCs of poor quality primarily due to halide vacancies on the surface. The use of additional iodide precursors during synthesis is known to improve the phase stability and PL of the NCs. ,,, The doping of metal ions − and surface treatment by coordinating ligands ,,− are also effective approaches to obtaining highly luminescent and stable CsPbI 3 NCs. However, despite intense investigations, phase-stable and highly luminescent CsPbI 3 NCs with suppressed PL blinking are still not known.…”

Passivation Layer of Potassium Iodide Yielding High Efficiency and Stable Deep Red Perovskite Light-Emitting Diodes

“…Many useful works have been made to enhance the performance of the CsPbI 3 NC emissive layer (EML) to improve the efficiency and stability of PeLEDs. For example, doping metal ions, such as Ag + , Zn 2+ , Cu 2+ , Ni 2+ , Mg 2+ , In 3+ , Y 3+ , and Zr 4+ , can enhance the crystal formation energy of NCs and thus improve their optical properties and structural stability. − ,− Especially, in our previous work, Sr-doped CsPbI 3 NCs showed near-unity PLQY, and the EQE of the PeLED was increased up to 17.1% . In addition, the surface passivation strategy was also applied to improve the photoluminescence (PL) properties and reliability of CsPbI 3 NCs. − For example, when CsPbI 3 NCs are passivated by 2,2′-iminodibenzonic acid (IDA), they show near-unity PLQY and improved stability due to an increased surface binding energy, which in turn largely improves the maximum EQE of PeLEDs .…”