Ou Xu,Xiaoyan Lu,Xiaodong Shen,Tongzhou Li,Bao Ke,Jialong Zhao,Bingsuo Zou
CsPbBr 3 nanocrystals (NCs) have attracted extensive attention due to their high color purity and good thermal stability. However, due to the quenching of surface defects, the photoluminescence quantum yields (PLQY) are low, and there are few previous comparative studies on the magnetic ion doping of powders and nanocrystals in this system. In this article, the effect of Cr 3+ doping CsPbBr 3 NCs and CsPbBr 3 powders and their PL properties is investigated. The successful doping of Cr 3+ is verified by TEM, SEM, and EDS characterization. At the appropriate amount of Cr 3+ , the PLQY of Cr 3+ doped CsPbBr 3 NCs achieves 96%, twice that of undoped CsPbBr 3 NCs. However, the PLQY of the CsPbBr 3 powder does not change much after Cr 3+ doping at its close emission wavelength. The electron paramagnetic resonance (EPR), temperature dependent PL and density functional theory (DFT) calculation show that the enhanced PL of doped CsPbBr 3 NCs is due to the formation of exciton magnetic polaron (EMPs), while the confined excitons in undoped NCs are multiple due to spin-orbit interaction. In CsPbBr 3 powders, both EMPs and antiferromagnetic excitons (AMPs) coexist and compete, verified by the PL decay curve, temperature variation spectra, and low temperature PL spectra in strong magnetic field.
Bingsuo Zou,Lipeng Hou,Ye Tian,Junbo Han,Hui Peng,Xiongtao Yang,Lijie Shi
The magnetic excitons in diluted magnetic semiconductor (DMS) have varied formats due to the inhomogeneous phases out of doping concentration and/or structural relaxations or defects. Here the high quality cobalt-doped zinc blende ZnSe nanoribbons (NRs) were synthesized, showing bright and color-variable emissions from blue, yellow to a little mixed white colors. Their power and temperature dependent micro-photoluminescence (PL) spectra have been obtained in which two emission bands, one magnetic exciton band near the band-edge and a Co2+ high-level d–d transition emission band at 550 nm out of their ferromagnetic (FM) coupled aggregates in ZnSe lattice, both bands could also be reflected by a nonlinear optical absorption enhancement. The easy formed stacking fault defects in a chemical vapor deposition (CVD) grown ZnSe zincblende NR took part in the above optical processes out of magnetic polaronic excitons (PXs). The femtosecond (fs) laser pulse pumping on single ZnSe:Co NR produces obvious lasing behavior but with profile of a complicated magnetic exciton interactions with indication of a crossover from collective exciton magnetic polarons (EMP) to bound magnetic polaron (BMP) scattering in Co doped ZnSe NR. These findings indicate the complication of the magnetic coupling natures in varied DMS structures, whose optical properties have been found to be highly nonlinear, due to the involvement of the spin–spin, spin–exciton and spin–phonon interactions, verified by the theoretic calculation in Yang X-T et al (2019 Interstitial Zn-modulated ferromagnetism in Co-doped ZnSe Mater. Res. Express 6 106121).
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