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Single-photon superradiance in individual cesium lead halide quantum dots
(2023)Research SquareThe brightness of an emitter is ultimately described by Fermi’s golden rule, with a radiative rate proportional to its oscillator strength times the local density of photonic states (LDOS). Since the oscillator strength is an intrinsic material property, the quest for ever brighter emission has relied on LDOS engineering, via dielectric or plasmonic resonators1,2. In contrast, a much less explored avenue is to boost the oscillator strength, ...Working Paper -
Scaling of Hybrid QDs-Graphene Photodetectors to Subwavelength Dimension
(2023)arXivEmerging colloidal quantum dot (cQD) photodetectors currently challenge established state-of-the-art infrared photodetectors in response speed, spectral tunability, simplicity of solution processable fabrication, and integration onto curved or flexible substrates. Hybrid phototransistors based on 2D materials and cQDs, in particular, are promising due to their inherent photogain enabling direct photosignal enhancement. The photogain is ...Working Paper -
Colloidal aziridinium lead bromide quantum dots
(2023)Research SquareThe compositional engineering of lead-halide perovskite nanocrystals (NCs) via the A-site cation represents a lever to fine-tune their structural and electronic properties. However, the presently available chemical space remains minimal since, thus far, only three A-site cations have been reported to favor the formation of stable lead-halide perovskite NCs, i.e., Cs⁺ , formamidinium (FA), and methylammonium (MA). Inspired by recent reports ...Working Paper -
Designer Phospholipid Capping Ligands for Soft Metal Halide Nanocrystals
(2023)Research SquareThe success of colloidal semiconductor nanocrystals (NCs) in science and optoelectronics is inextricable from their surfaces. The functionalization of lead halide perovskite (LHP) NCs poses a formidable challenge due to their structural lability, unlike the well-established covalent ligandcapping of conventional semiconductor NCs. We posited that the vast and facile molecular engineering of phospholipids as zwitterionic surfactants can ...Working Paper -
Disentangling the Effects of Structure and Lone-Pair Electrons in the Lattice Dynamics of Halide Perovskites
(2023)arXivMetal halide perovskites have shown great performance as solar energy materials, but their outstanding optoelectronic properties are paired with unusually strong anharmonic effects. It has been proposed that this intriguing combination of properties derives from the "lone pair" electrons of the octahedral metal cations, but the precise impact of this chemical feature remains unclear. Here we show that in fact a lone pair of electrons is ...Working Paper -
Persistent Enhancement of Exciton Diffusivity in CsPbBr3 Nanocrystal Solids
(2022)arXivIn semiconductors, exciton or charge carrier diffusivity is typically described as an inherent material property. Here, we show that the transport of excitons (i.e., bound electron-hole pairs) in CsPbBr3 perovskite nanocrystals (NCs) depends markedly on how recently those NCs were occupied by a previous exciton. Using fluence- and repetition-rate-dependent transient photoluminescence microscopy, we visualize the effect of excitation ...Working Paper -
Phonon-Mediated Attractive Interactions between Excitons in Lead-Halide-Perovskites
(2022)arXivUnderstanding the origin of electron-phonon coupling in lead-halide perovskites (LHP) is key to interpreting and leveraging their optical and electronic properties. Here we perform femtosecond-resolved, optical-pump, electron-diffraction-probe measurements to quantify the lattice reorganization occurring as a result of photoexcitation in LHP nanocrystals. Photoexcitation is found to drive a reduction in lead-halide octahedra tilts and ...Working Paper -
Stable near-to-ideal performance of a solution-grown single-crystal perovskite X-ray detector
(2021)Research SquareThe ideal photodetector is the one able to detect every single incoming photon. In particular, in X-ray medical imaging, the radiation dose for patients can then approach its fundamentally lowest limit set by the Poisson photon statistics. Such near-to-ideal X-ray detection characteristics have been demonstrated with only a few semiconductor materials such as Si1 and CdTe2; however, their industrial deployment in medical diagnostics is ...Working Paper -
On the Feasibility of All-solid-state Batteries with LLZO as a Single Electrolyte
(2021)Research SquareReplacement of Li-ion liquid-state electrolytes by solid-state counterparts in a Li-ion battery (LIB) is a major research objective as well as an urgent priority for the industry, as it enables the use of a Li metal anode and provides new opportunities to realize safe, non-flammable, and temperature-resilient batteries. Among the plethora of solid-state electrolytes (SSEs) investigated, garnet-type Li-ion electrolytes based on cubic ...Working Paper