Wenchao Wang,Xueqin Bai,Qing Ci,Lili Du,Xingang Ren,David Lee Phillips
Undesired photoelectronic dormancy through active species decay is adverse to photoactivity enhancement. An insufficient extrinsic driving force leads to ultrafast deep charge trapping and photoactive species depopulation in carbon nitride (g-C 3 N 4 ). Excitation of shallow trapping in g-C 3 N 4 with long-lived excited states opens up the possibility of pursuing high-efficiency photocatalysis. Herein, a near-field-assisted model is constructed consisting of an In 2 O 3 -cube/g-C 3 N 4 heterojunction associated with ultrafast photodynamic coupling. This In 2 O 3 -cube-induced near-field assistance system provides catalytic “hot areas”, efficiently enhances the lifetimes of excited states and shallow trapping in g-C 3 N 4 and this favors an increased active species density. Optical simulations combined with time-resolved transient absorption spectroscopy shows there is a built-in charge transfer and the active species lifetimes are longer in the In 2 O 3 -cube/g-C 3 N 4 hybrid. Besides these properties, the estimated overpotential and interfacial kinetics of the In 2 O 3 -cube/g-C 3 N 4 hybrid co-promotes the liquid phase reaction and also helps in boosting the photocatalytic performance. The photocatalytic results exhibit a tremendous improvement (34-fold) for visible-light-driven hydrogen production. Near-field-assisted long-lived active species and the influences of trap states is a novel finding for enhancing (g-C 3 N 4 )-based photocatalytic performance.
Ju-Ping Ma,Ya-Meng Chen,Lu-Min Zhang,Shao-Qiang Guo,Jian-Dang Liu,Hong Li,Bang-Jiao Ye,Zhi-Yong Li,Yang Zhou,Bin-Bin Zhang,Osman M. Bakr,Jun-Ying Zhang,Hong-Tao Sun
Doping has been established as a powerful approach for endowing lead halide perovskite nanocrystals (NCs) with novel properties. However, our fundamental understanding of the local structure of dopants, doping efficiency and luminescence properties of these NCs is still very sparse. Here, we provide the first experimental evidence regarding the local structure of rare earth ions in CsPbCl3 NCs, based on the analysis of extended X-ray absorption fine structure spectroscopy. Our result suggests that Yb3+ occupies the Pb2+ crystallographic sites in CsPbCl3 NCs. We further demonstrate a strategy to examine the determinant of the doping efficiency in lanthanide-doped lead halide perovskite NCs, which enables us to uncover the important role of structural defects in affecting the doping efficiency. A broad range of experimental characterization techniques including steady-state and time-resolved luminescence spectra, X-ray absorption spectra, and positron annihilation lifetime spectra, coupled with first-principles calculations, help us identify that the doping efficiency is associated with structural defects in NCs and that the formation of a higher-concentration of defects favors incorporation of a higher-concentration of dopants into the lattice. Importantly, we demonstrate that the concept of defect-assisted doping is not limited to the model system of Yb3+-doped CsPbCl3 NCs, but can be used as a guideline to rationally tune the doping efficiency of lanthanide-doped halide perovskite NCs. We also show that lanthanide-doped CsPbCl3 NCs demonstrate anomalous decay of the band-edge emission, which we propose is due to the existence of shallow trapping states near the conduction band. Our results greatly deepen the understanding of the structural and photophysical properties of lanthanide-doped lead halide perovskite NCs, and highlight the possibility to use the chemistry of defects to tailor the doping efficiency of halide perovskite NCs.
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