II–VI
two-dimensional (2D) nanoplatelets (NPLs) exhibit
the narrowest optical features among nanocrystals (NCs). This property
remains true for Hg-based NPLs, despite a cation exchange procedure
to obtain them from Cd-based NPLs, which leads to structural defects
(poorly defined edges and voids) inducing inhomogeneous broadening.
Here, we propose an optimized procedure for which a solvent, surface
chemistry, and reaction conditions are rationally considered. The
procedure is applied to the growth of alloyed HgSe1–x
Te
x
NPLs with various
compositions. We report a bright photoluminescence for all compositions.
Structural properties being now well defined, it is possible to study
the electronic properties of these objects. To do so, we combine k·p
modeling of quantum-confined structures with X-ray photoemission.
In particular, we clarify the origin of the similarity between CdTe
and HgTe NPLs absorption spectra despite their vastly differing bulk
band structures. Finally, static- and time-resolved photoemission
unveil a crossover from n- to p-type behavior in HgSe1–x
Te
x
NPLs while increasing
the Te content.
The interest in perovskite nanocrystals (NCs) such as CsPbBr 3 for quantum applications is rapidly raising, as it has been demonstrated that they can behave as very efficient single photon emitters. The main problem to tackle in this context is their photostability under optical excitation. In this article, we present a full analysis of the optical and quantum properties of highly efficient perovskite nanocubes synthesized with an established method, which is used for the first time to produce quantum emitters and is shown to ensure increased photostability. These emitters exhibit reduced blinking together with a strong photon antibunching. Remarkably these features are hardly affected by the increase of the excitation intensity well above the emission saturation levels. Finally, we achieve for the first time the coupling of a single perovskite nanocube with a tapered optical nanofiber in order to aim for a compact integrated single photon source for future applications.
Nanocrystals (NCs) have reached a high level of maturity, enabling their integration into optoelectronic devices. The next challenge is the combination of several types of devices into one complex system to achieve better on‐chip integration. Here, an all‐HgTe‐NC active imaging setup operating in the short‐wave infrared (IR) is focused on. First, the design of an optimized IR light‐emitting diode (LED) is focused on. It is shown that a halide technology processing enables an increase of the electroluminescence signal by a factor of 3, while preserving a low turn‐on voltage and a high brightness (3 W sr−1 m−2). Then the degradation mechanism of this LED under continuous operation is unveiled and a shift from band edge to trap emission is shown. This degradation process can be strongly reduced thanks to the encapsulation and the thermal control of the LED. Lastly, the IR emission of the LED is imaged using a focal plane array whose active layer is also made of HgTe NCs, paving the way for all‐NC‐based active imaging setups.
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