Perovskite Quantum Dots for Super‐Resolution Optical Microscopy: Where Strong Photoluminescence Blinking Matters

Blinking nanoscale emitters, typically single molecules, are employed in single‐molecule localization microscopy (SMLM), such as direct stochastic optical reconstruction microscopy (dSTORM), to overcome Abbe's diffraction limit, offering spatial resolution of few tens of nanometers. Colloidal quantum dots (QDs) feature high photostability, ultrahigh absorption cross‐sections and brightness, as well as wide tunability of the emission properties, making them a compelling alternative to organic molecules. Here, CsPbBr3 nanocrystals, the latest addition to the QD family, are explored as probes in SMLM. Because of the strongly suppressed QD photoluminescence blinking (ON/OFF occurrence higher than 90%), it is difficult to resolve emitters with overlapping point‐spread functions by standard dSTORM methods due to false localizations. A new workflow based on ellipticity filtering efficiently identifies false localizations and allows the precise localization of QDs with subwavelength spatial resolution. Aided by Monte‐Carlo simulations, the optimal QD blinking dynamics for dSTORM applications is identified, harnessing the benefits of higher QD absorption cross‐section and the enhanced QD photostability to further expand the field of QD super‐resolution microscopy toward sub‐nanometer spatial resolution. Fluorescence probes with high photostability and bright emission are in high demand for super‐resolution microscopy. Perovskite quantum dots meet these requirements, but suffer from nonoptimal blinking statistics. A new workflow based on ellipticity filtering proves to be efficient in identifying the large fraction of false localizations. The engineerability of perovskite quantum dots can now be exploited toward sub‐nanometer spatial resolution.