Traditional infrared (IR) technology has relied on the epitaxial growth of CdHgTe (MCT) and InGaAs since 1960s. 
While these epitaxial materials are well-established, they have not become cost-effective products for the consumer 
market, limiting their applications. Solution-processed nanocrystals (NCs) exhibit tunable optical properties 
spanning from the UV to THz spectra, making them suitable for applications such as single photon emission, 
biolabeling, and down conversion for displays. Although the visible spectrum is commonly utilized, the potential of 
NCs in the IR range has been largely overlooked. For the infrared spectral range, organic semiconductors are 
intrinsically inefficient, leaving inorganic NCs as the most cost-effective and efficient option. Here, we present our 
latest achievements in infrared light-emitting diodes (LEDs) and photodiodes (PDs), operating across various 
wavelengths using tunable emissive colloidal materials. Our focus has been on CdHgSe nanoplatelets (NPLs) and
RoHS-compliant InAs quantum dots (QDs).
Mercury chalcogenides (eg. HgSe and HgTe) exhibit the most efficient emission in the near-IR to mid-IR range. 
However, these materials are inherently fragile, making it extremely challenging to grow a shell over them. To 
address this, we developed an innovative synthesis method starting with CdSe NPLs. We performed cation 
exchange, replacing Cd with Hg, and subsequently grew a thick layer of CdZnS over the resulting Cd_xHg_1-xSe NPLs. 
This procedure allows fine tuning by adjusting the concentration of Hg cations and the stoichiometric ratio of Cd/Hg, 
mirroring the epitaxial growth of MCT. Utilizing this tunable short-wave infrared (SWIR) emitting material, which 
achieves a photoluminescence quantum yield (PLQY) of 55%, we designed and fabricated LEDs that emit at 
wavelengths ranging from 1200 nm to 1700 nm. This builds on our previous work, where we achieved an external 
quantum efficiency (EQE) of 7.5% at 1300 nm. [1] Here, we also showed the potential of using the same material as 
the active layer of PD, with an EQE of 25% at 1200 nm wavelength.
In parallel, with an innovative synthesis of InAs/ZnSe core/shell QDs we increased the thickness of ZnSe thick shell. 
Synthesizing InAs QDs has traditionally been a complex process, typically requiring the use of highly reactive, 
flammable, toxic, and expensive chemicals such as tris-trimethylsilyl arsine (TMS-As). In recent years, researchers 
have sought to replace TMS-As with cheaper, safer, and less reactive arsenic precursors. Among the alternatives 
explored, tris(dimethylamino)-arsine (amino-As) has shown the most promise. Using amino-As along with Alane 
N,N-dimethylethylamine as a reducing agent and ZnCl₂ as an additive, we developed a method to synthesize InAs 
QDs and InAs/ZnSe core/shell QDs with a shell thickness 1.5 monolayers. These QDs exhibit photoluminescence (PL) at 860 nm and a PLQY of 42% ± 4%.[2] Utilizing these QDs, we produced an LED with a turn-on voltage of 2.7V, an EQE of 5.5%, and a maximum radiance of 0.2 Wsr⁻¹cm⁻². [3] Building on these findings, we refined our synthesis 
process to create InAs/ZnSe QDs with a tunable ZnSe shell thickness of up to 7 monolayers, achieving a remarkable 
PLQY of approximately up to 70% ± 7% and a PL peak at 900 nm in solution. [4] The electronic structure of the thickshell QDs resembles that of type-I heterostructures, enhancing exciton confinement in the core region due to the ZnSe layer. We utilized these efficient QDs for making LEDs. The champion LED reaches an EQE of 13.3% and radiance of 12 Wsr⁻¹cm⁻², figures-of-merit that are comparable to devices based on complex core/multi-shell InAs QDs obtained via a tris-trimethylsilyl (TMS) arsine route. [5]