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High fidelity single photon sources are required for the implementation of quantum information processing and communications protocols. Although colloidal quantum dots (CQDs) are single photon sources, their efficacy is limited by their tendency to show finite multiphoton emission at higher excitation powers. Here, we show that wave function engineering of CQDs enables the realization of emitters with significantly improved single photon emission performance. We study the ZnS/CdSe/CdS system. It is shown that this system offers significantly improved probabilities of single photon emission. While conventional CQDs such as CdSe/CdS exhibit a g2(0) > 0.5 ± 0.02 at ⟨N⟩ = 2.17, ZnS/CdSe/CdS show a greatly improved g2(0) ≈ 0.04 ± 0.01. Improved single photon emission performance encourages the use of colloidal materials as quantum light sources in emerging quantum devices. [ABSTRACT FROM AUTHOR]

Inherent disorder in perovskite films has been suggested as a factor that improves exciton separation. At the same time, the disorder can potentially disrupt electron flow, deteriorating device performance. In this paper, we study the role of disorder in electron transport in perovskite films using kinetic Monte Carlo simulations. The effect of temperature on the conductivity of the system is studied. We find that at room temperature, where most solar cells operate, the effect of disorder on the conductivity is minimal. At lower temperatures, current flows along specific paths in the film. In contrast, the ability of carriers to sample all sites in the film at room temperature allows realisation of higher device efficiencies. We find that conductivity obeys Mott's expression for variable range hopping σ(T) ∝ T−1e−(To/T)1/3. The value of the universal proportionality constant α2 associated with the characteristic temperature has been computed. The effect of electric field on transport has also been studied. The average hopping distance is found to increase with the increase in the electric field at low temperatures, although this dependence is not observed at room temperature. Likewise, the conductivity is also a function of applied field F, and is found to be obey σ(F) ∝ F−1/3e−(Fo/F)1/3 at low temperatures while being field-independent at room temperature. [ABSTRACT FROM AUTHOR]

Microbolometers have emerged as a cost‐effective alternative to cooled infrared photon detectors, albeit with certain trade‐offs in terms of responsivity (Rλ$R_{\lambda}$), detectivity (D*$D_{\*}$), and response time (tr$t_{\text{r}}$). The research in this field is driven by the potential applications in night vision devices, military surveillance, and autonomous vehicles, leading to a growing interest in exploring new materials to bridge the performance gap between cooled photon detectors and uncooled bolometers. This study focuses on the optoelectronic and bolometric characteristics of CuFeSe2$\left(\text{CuFeSe}\right)_{2}$ nanocrystals (NCs) in a colloidal solution. These NCs exhibit a significant change in resistivity (ρ) when subjected to temperature variations ranging from 170 to 400 K. Specifically, the temperature coefficient of resistance (TCR), α, is 1.9% per Kelvin for a room temperature resistivity of 505 Ω cm. Furthermore, the responsivity of CuFeSe2$\left(\text{CuFeSe}\right)_{2}$ NCs is reported to be 0.101 A W−1, and the Hall mobility of the colloidal solution is determined as 0.1 cm2 V s−1$0 \text{.1} \textrm{ } \left(\text{cm}\right)^{2} \textrm{ } \text{V} \textrm{ } \left(\text{s}\right)^{- 1}$. Finally, a comprehensive comparison is conducted between the performance metrics of established bolometer materials, such as VOx and a‐Si, and those of colloidal CuFeSe2$\left(\text{CuFeSe}\right)_{2}$ NCs. Based on the results, colloidal CuFeSe2$\left(\text{CuFeSe}\right)_{2}$ NCs are a promising option for future bolometer technology. [ABSTRACT FROM AUTHOR]

Photonic devices stand to benefit from the development of chromophores with tunable, precisely controlled spontaneous emission lifetimes. Here, we demonstrate a method to continuously tune the radiative emission lifetimes of a class of chromophores by varying the density of electronic states involved in the emission process. In particular, we examined the peculiar composition-dependent electronic structure of copper doped CdZnSe quantum dots. It is shown that the nature and density of electronic states involved with the emission process is a function of copper inclusion level, providing a very direct handle for controlling the spontaneous lifetimes. The spontaneous emission lifetimes are estimated by examining the ratios of emission lifetimes to absolute quantum yields and also measured directly by ultrafast luminescence upconversion experiments. We find excellent agreement between these classes of experiments. This scheme enables us to tune spontaneous emission lifetimes by three orders of magnitude from ∼15 ns to over ∼7 µs, which is unprecedented in existing lumophores. [ABSTRACT FROM AUTHOR]

Auâ€"Ag nanostructures comprising of ∼1 nm Ag nanoparticles embedded into an Au matrix show several unconventional optical, electric and magnetic properties. Here, we review progress made towards the preparation of these materials as well as analysis of their structure. Further, electrical and magnetic transitions in these materials are discussed. Finally, we review the properties of these materials as revealed from optical and electron microscopic probes. [ABSTRACT FROM AUTHOR]

CuAlS2/ZnS Quantum dots (QDs) are known to directly convert aqueous solutions of bicarbonate ions to oxygen and organic molecules such as formate with a remarkable efficiency even under sunlight. In cases, fairly complicated organic reaction products such as acetate and methanol have been observed when reactions are allowed to continue for longer periods of time. Here, we investigate the electron dynamics that occurs within CuAlS2/ZnS QDs and show that it is essentially dominated by ultrafast electron transfer (560 fs for 0.4 excitons per dot) to the surface. The electron dwell time in the conduction band increases exponentially (for example 872 fs for 1.4 excitons per dot) with the excitation fluence. This is reverse of the auger limited response of conventional QDs and is hypothesized to exhibit strong charge separation that lies at the root of the remarkable photocatalytic activity. We further investigate this system through multi‐pump experiments. We find that the system response to prior excitation changes over the period of nanoseconds, consistent with the charge reorganization in the system, well after the initial electron transfer. The results of these experiments are summarized in terms of a coulomb‐well interpretation. [ABSTRACT FROM AUTHOR]