Optimized Cation Exchange for Mercury Chalcogenide 2D Nanoplatelets and Its Application for Alloys

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–xTex 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–xTex NPLs while increasing the Te content. The project was supported by ERC starting grants Ne2DeM (grant no 853049) and blackQD (grant no 756225). The authors acknowledge the use of clean-room facilities at the “Centrale de Proximité Paris-Centre”. This work was supported by Region Ile-de-France in the framework of DIM Nano-K (grant dopQD). This work was also supported by French state funds managed by the ANR within the Investissements d’Avenir programme under reference ANR-11-IDEX-0004-02 and, more specifically, within the framework of the Cluster of Excellence MATISSE and by grants IPER-Nano2 (ANR-18CE30-0023-01), Copin (ANR-19-CE24-0022), Frontal (ANR-19-CE09-0017), Graskop (ANR-19-CE09-0026), NITQuantum (ANR-20-ASTR-0008-01), Bright (ANR-21-CE24-0012-02), and MixDferro (ANR-21-CE09-0029). A.C. thanks Agence Innovation Defense for Ph.D. funding. J.P. and J.I.C. acknowledge support from Prometeo Grant Q-Devices (Prometeo/2018/098).