Perovskite quantum dots (QDs) as a new type of colloidal nanocrystals (NCs) have gained significant attention for both fundamental research and applications of optoelectronic devices owing to their appealing optoelectronic properties and excellent chemical processability. For their wide range of potential applications, synthesizing colloidal QDs with high crystal quality and stability is of crucial importance. However, like most common QD systems, those reported perovskite QDs still suffer from a certain density of trapping defects, giving rise to detrimental non-radiative recombination centers and thus quenching luminescence. Very recently, we have suceeded in synthesis of phase stable and less defect preovksite QDs, including APbX3 NCs (A: FA, MA, Cs; X: I, Br, Cl), Sn-Pb alloyed NCs and Sn-based NCs [1-7]. We have demonstrated that a high room-temperature photoluminescence quantum yield (PL QY) of close to 100% can be obtained in the APbX3 perovskite QDs, signifying the achievement of ignorable less trapping defects in the APbX3 QDs. Ultrafast kinetic analysis with time-resolved transient absorption spectroscopy evidences the negligible electron or hole trapping pathways in our QDs, which explains such a high quantum efficiency. In addtion, photoexcited hot and cold carrier dynamics as well as charge transfer at the heterojunction of QD/metal oxide were systematically investigated [4]. Solar cells based on these high-quality perovskite QDs exhibit power conversion efficiency of over 15%, showing great promise for practical application. On the other hand, through incorporation of alkali ion Na+, we have realized for the first time efficient near-infrared emission from highly defective Sn-Pb perovskite QDs with substantially improved PL QY from ~0.3% to 28% [5]. Our findings provide new insights into the materials design strategies for improved optoelectronic properties of Sn-containing perovskites. We anticipate their use in near-infrared devices is very promising if issues of the sustainability of PL QY can be fully addressed in the near future.

References

1. F. Liu and Q. Shen et al., ACS Nano 11 (2017) 10373

2. F. Liu and Q. Shen et al., J. Am. Chem. Soc. (2017) 139, 16708

3. F. Liu and Q. Shen et al., Chem. Mater. 32 (2020) 1089

4. C. Ding and Q. Shen et al., Nano Energy 67 (2020) 104267

5. F. Liu and Q. Shen et al., Angew. Chem. Int. Ed. 59 (2020) 8421

6. J. Jiang, F. Liu, Q. Shen and SX. Tao, J. Mater. Chem. A 9 (2021) 12087

7. F. Liu and Q. Shen et al., ACS Appl. Nano Mater. 4 (2021) 3958