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Quantum cutting (QC) allows the conversion of high-energy photons into lower-energy photons, exhibiting great potential for infrared communications. Yb-doped perovskite nanocrystals can achieve an efficient QC process with extremely high photoluminescence quantum yield (PLQY) thanks to the favorable Yb 3+ incorporation in the perovskite structure. However, conventionally used oleic acid-oleylamine-based ligand pairs cause instability issues due to highly dynamic binding to surface states that have curbed their potential applications. Herein, zwitterionic type C3-sulfobetaine 3-(N,N-Dimethylpalmitylammonio)propanesulfonate molecule is utilized to build a strong binding state on the nanocrystals' surface through a new phosphine oxide synthesis route. Leveraging machine learning and Bayesian Optimization workflow to determine optimal synthesis conditions, near-infrared PLQY above 190% is achieved. The high PLQY is well maintained after over three months of aging, under high-flux continuous UV irradiation, and long continuous annealing. This is the first report of highly efficient and stable perovskite quantum cutters, which will drive the study of fundamental physics phenomena and near-infrared quantum communications., (© 2024 Wiley‐VCH GmbH.)

Colloidal perovskite quantum dots (PQDs) have emerged as highly promising single photon emitters for quantum information applications. Presently, most strategies have focused on leveraging quantum confinement to increase the nonradiative Auger recombination (AR) rate to enhance single-photon (SP) purity in all-inorganic CsPbBr 3 QDs. However, this also increases the fluorescence intermittency. Achieving high SP purity and blinking mitigation simultaneously remains a significant challenge. Here, we transcend this limitation with room-temperature synthesized weakly confined hybrid organic-inorganic perovskite (HOIP) QDs. Superior single photon purity with a low g (2) (0) < 0.07 ± 0.03 and a nearly blinking-free behavior (ON-state fraction >95%) in 11 nm FAPbBr 3 QDs are achieved at room temperature, attributed to their long exciton lifetimes ( τ X ) and short biexciton lifetimes ( τ XX ). The significance of the organic A-cation is further validated using the mixed-cation FA x Cs 1- x PbBr 3 . Theoretical calculations utilizing a combination of the Bethe-Salpeter (BSE) and k·p approaches point toward the modulation of the dielectric constants by the organic cations. Importantly, our findings provide valuable insights into an additional lever for engineering facile-synthesized room-temperature PQD single photon sources.

The field screening effect on the field-emission properties of armchair graphene nanoribbons (AGNRs) under strain has been studied using first-principles calculations with local density approximation (LDA). Using the zone folding method with the effect of a dipole barrier along with the work function of strained graphene, we can obtain the work function of AGNR of any width under strain, confirmed with the LDA calculations. We have systematically investigated the effects of inter-ribbon distance and ribbon width on the work function of AGNR arrays. It is found that the work function of AGNR arrays increases rapidly as the inter-ribbon distance D x increases, which is caused by the positive dipole at the edge of the ribbon. Using a simple linear interpolation model, we can obtain the work function of AGNRs of any ribbon-width and inter-ribbon distance. The dependences of the inter-ribbon distance and strain on the field enhancement factor have been determined. The enhancement factor reaches about 90% of its saturated value as the inter-ribbon distance approaches two times the ribbon-width. For a tensile strain, the field enhancement factor increases with applied strain while for a compressive one, the field enhancement factor is nearly independent. The effects of inter-ribbon distance and strain on the enhancement factor can be explained by the interlayer and intralayer screening effects, respectively., Competing Interests: The authors declare no competing financial interests., (This journal is © The Royal Society of Chemistry.)