Scanning the optoelectronic properties of Cs4CuxAg2-2xSb2Cl12 double perovskite nanocrystals: the role of Cu2+ content

Double perovskite nanocrystals (NCs) have attracted much attention owing to their non-toxicity and excellent semiconducting characteristics. Herein, a series of double perovskite Cs4CuxAg2-2xSb2Cl12 NCs (x = 0.60, 0.75, 0.90, and 1.00) have been synthesized and the relationship between the Cu2+ content and their photo-physical properties has been investigated in detail. The temperature-dependent absorption data point out that the Cu2+ content can affect the transition from the indirect to direct band gap, but hardly influence the evolution of the band edge at different temperatures, which almost linearly red shifts with temperature. The transient absorption technique helps us to obtain the absorption coefficient of these double perovskite NCs. The linear and three-order nonlinear absorption coefficients, which are first measured by transient absorption (TA) and Z-scan techniques, apparently decrease with the Cu2+ content. Intensity-dependent TA curves offer their carrier recombination rate constants (involving the mono-molecular (k(1)), bi-molecular (k(2)) and Auger recombination (k(3)) rate constants). Herein, k(1) decreases with the Cu2+ content owing to the variance of Cu-Cl bonds in the x-y plane, but k(2) and k(3) show an opposite trend. The current-voltage test with strong light bias confirms that the monomolecular recombination is dominant in the operation of photo-detectors based on Cs4CuxAg2-2xSb2Cl12 NC films and the light-harvesting ability should be responsible for the photocurrent of the photo-detector. Our results provide a comprehensive insight into the optoelectronic properties of these double perovskite NCs.

Automated summary

Double perovskite nanocrystals have gained much attention due to their non-toxicity and excellent semiconductor properties. In this study, a series of Cs4CuxAg2-2xSb2Cl12 nanocrystals with different Cu2+ contents were synthesized, and the relationship between Cu2+ content and their photo-physical properties was investigated. The results showed that Cu2+ content can affect the band gap transition and absorption coefficient of the nanocrystals, which in turn influences the operation of photo-detectors.