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

Abstract

HgTe colloidal nanocrystals (NCs) have become a promising building block for infrared optoelectronics. Despite their cubic zinc blende lattice, HgTe NCs tend to grow in a multipodic fashion, leading to poor shape and size control. Strategies to obtain HgTe NCs with well-controlled sizes and shapes remain limited and sometimes challenging to handle, increasing the need for a new growth process. Here, we explore a synthetic route via seeded growth. In this approach, the small HgTe seeds are nucleated in the first step, and they show narrow and bright photoluminescence with 75% quantum yield in the near infrared region. Once integrated into Light emitting diodes (LEDs), these seeds lead to devices with high radiance up to 20 WSr -1 m -2 and a long lifetime. Heating HgTe seeds formed at the early stage leads to the formation of sphere-shaped HgTe with tunable band edges from 2 to 4 µm. Last, the electronic transport tests conducted on sphere-shaped HgTe NC arrays reveals enhanced mobility and stronger temperature dependence than the multipodic shaped particles.

Bias Tunable Spectral Response of Nanocrystal Array in a Plasmonic Cavity

“…We design a device based on HgTe NCs. The latter are grown using the Prado et al procedure . Briefly, HgBr 2 and TOP:Te are mixed at room temperature and react to form seeds that later grow when heated in a hot oleylamine solution.…”

“…The latter are grown using the Prado et al procedure. 27 Briefly, HgBr 2 and TOP:Te are mixed at room temperature and react to form seeds that later grow when heated in a hot oleylamine solution. TEM observations (Figures 1b and S1) show that the obtained particles have a slightly faceted spherical shape, with a typical diameter close to 10 nm.…”

Electroluminescence from nanocrystals above 2 µm

“…Despite their poor shape control, these branched HgTe NCs present a narrower band-edge feature compared to spherical NCs. 18,19 These HgTe NCs are photoluminescent, see Figure 1a-b. The PL signal is red shifted by 120 nm from the absorption maximum due to Stokes' shift.…”

Correlating Structure and Detection Properties in HgTe Nanocrystal Films

“…Beyond the formation of traps, the multipodic shape particles may also induce a poor particle packing within the film, resulting in a distribution of interparticule distances that consequently limits the film mobility and generates noise . Only recently has the growth of quasi spherical HgTe CQDs been achieved, , which has reduced the size distribution and has finally led to improved film mobilities higher than 1 cm 2 V –1 s –1 . , However, their spectra are broader than the ones obtained from multipodic HgTe, in spite of a better size control . It is thus of utmost interest to reveal how the shape is linked to the performance obtained so far for IR detection.…”