Electroluminescence from HgTe Nanocrystals and Its Use for Active Imaging

Abstract

Mercury telluride (HgTe) nanocrystals are among of the most versatile infrared (IR) materials with the absorption of first optical absorption which can be tuned from visible to the THz range. Therefore, they have been extensively considered as near IR emitters and as absorbers for low-cost IR detectors. However, the electroluminescence of HgTe remains poorly investigated in spite of its ability to go toward longer wavelengths compared to traditional lead sulfide (PbS). Here, we demonstrate a light emitting diode (LED) based on an indium tin oxide (ITO)/zinc oxide (ZnO)/ZnO-HgTe/PbS/gold stacked structure, where the emitting layer consists of a ZnO/HgTe bulk heterojunction which drives the charge balance in the system. This LED has low turn-on voltage, long lifetime, and high brightness. Finally, we conduct short wavelength infrared (SWIR) active imaging, where illumination is obtained from a HgTe NC-based LED, and demonstrate moisture detection.

Seeded Growth of HgTe Nanocrystals for Shape Control and Their Use in Narrow Infrared Electroluminescence

“…The band gap of the PbS layer is chosen to be larger than that of HgTe so that the PbS layer does not behave as a recombination center. 45 The emitting layer is a bulk heterojunction where electron conduction is ensured by ZnO and hole conduction is ensured by HgTe. To make this layer conductive while preserving the PL signal, the initial long ligands are replaced by dipping the film into a solution of HgCl2 (see the SI).…”

Mercury Chalcogenide Quantum Dots: Material Perspective for Device Integration

“…Because NCs are continuously spectrally tunable, they offer higher flexibility for the design of IR emitting devices than their III-V counterparts obtained using epitaxy, the substrate-lattice matching for which reduces the bandgap tunability. Despite the development of HgX NCs, as reviewed in the following sections, this first targeted application remains undemonstrated, although certain recent reports [21][22][23] indicate that HgX NCs are promising materials to obtain infrared light sources. Moreover, considerable progress has been made in the control of the surface chemistry of NCs 4,[24][25][26] to obtain large carrier mobility films (µ≈1 cm 2 .V -1 .s -1 ), and the growth of HgX NCs with larger absorption wavelengths 3,[27][28][29][30] has led to the emergence of HgX NCs as a viable building block for low cost IR sensing.…”

Correlating Structure and Detection Properties in HgTe Nanocrystal Films

“…II-VI semiconductors are the most mature materials under colloidal quantum dot (CQD) form and have been extensively used for optoelectronic applications. Among them, HgTe is certainly offering the widest spectral tunability and the most impressive device performance for infrared light emission [1][2][3] and detection. [4][5][6] Over the recent years, the integration of HgTe CQDs as absorbing layers in IR sensors has been developed from the basic demonstration of IR photoconduction, 7,8 to highly complex devices including focal plane arrays [9][10][11][12][13] and unconventional detectors with enhanced light-matter coupling to increase their light absorption.…”