Lead halide perovskite quantum dots (QDs) are promising candidates for future optoelectronic devices due to their excellent photonic and electronic properties. However, poor stability and toxicity problems limit their further development. This work demonstrates the doping tactics to boost the optical properties of lead-free colloidal MA 3 Bi 2 Br 9 QDs, the indium ion (In 3+ ) doping presented herein is found to be effective in improving the photoluminescence (PL) properties of MA 3 Bi 2 Br 9 (CH 3 NH 2 = MA) QDs without alerting their favorable electronic structure. It has been elucidated by microscopy and diffraction results that the In 3+ doping optimizes the QDs solution octahedron structure, and the PL red-shifted phenomenon coincides well with the analogous red-shifted obtained in the ultraviolet/visible (UV–Vis) absorption spectroscopy, which is due to the quantum confinement effect. And the nanosecond transient absorption (ns-TA) spectroscopy elucidates that the enhanced radiative recombination process contributes to enhanced stability and luminescence. The photoluminescence quantum yield (PLQY) of MA 3 Bi 2 Br 9 QDs is increased by 60.7%. This work offers a valid strategy for improving the quality of the lead-free perovskite QDs.
Jian Zhang,Ying Yang,Hui Deng,Umar Farooq,Xiaokun Yang,Jahangeer Khan,Jiang Tang,Haisheng Song
Colloidal quantum dots (QDs) of lead halide perovskite have recently received great attention owing to their remarkable performances in optoelectronic applications. However, their wide applications are hindered from toxic lead element, which is not environment- and consumer-friendly. Herein, we utilized heterovalent substitution of divalent lead (Pb2+) with trivalent antimony (Sb3+) to synthesize stable and brightly luminescent Cs3Sb2Br9 QDs. The lead-free, full-inorganic QDs were fabricated by a modified ligand-assisted reprecipitation strategy. A photoluminescence quantum yield (PLQY) was determined to be 46% at 410 nm, which was superior to that of other reported halide perovskite QDs. The PL enhancement mechanism was unraveled by surface composition derived quantum-well band structure and their large exciton binding energy. The Br-rich surface and the observed 530 meV exciton binding energy were proposed to guarantee the efficient radiative recombination. In addition, we can also tune the inorganic perovskite QD (Cs3Sb2X9) emission wavelength from 370 to 560 nm via anion exchange reactions. The developed full-inorganic lead-free Sb-perovskite QDs with high PLQY and stable emission promise great potential for efficient emission candidates.
Tangxi Chen,Min Zhou,Wen Chen,Yuyao Zhang,Siyong Ou,Yueli Liu
Halide perovskite quantum dots (HP QDs) have been widely used in the field of photocatalysis due to their excellent performance. However, the issues of lead toxicity and instability prevent their process in the photocatalysis application. Herein, the lead-free Cs2AgInCl6 perovskite quantum dots (CAIC QDs) are synthesized by the hot-injection method, and CAIC QDs@Ag composites with various Ag loading amounts are self-assembled by adjusting the Cl source in the synthesis process, which is used to improve the CO2 photoreduction efficiency by using the surface plasmon resonance (SPR) effect of Ag nanoparticles. In addition, the surface ligand density of CAIC QDs@Ag composites is regulated by the purification processing treatment to release the influence of organic ligands on the charge transport performance. It is found that the CAIC QDs@Ag composite with the optimal ligands density possesses fast electron transport and effective carrier separation efficiency, which are crucial for the improvement of the photocatalysis reaction. As a result, the CAIC QDs@Ag-2 composite after purification processing achieves the highest yield of 26.4 μmol g−1 and 28.9 μmol g−1 for CO and CH4, respectively, during the CO2 photoreduction process. In addition, there is no significant decline of CO2 photoreduction performance after the photocatalysis cycling test for 9 h, indicating the good stability of the CAIC QDs@Ag composite in the photocatalysis process.
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