ZnCl₂ Mediated Synthesis of InAs Nanocrystals with Aminoarsine

Abstract

The most developed approaches for the synthesis of InAs nanocrystals (NCs) rely on pyrophoric, toxic, and not readily available tris-trimethylsilyl (or tris-trimethylgermil) arsine precursors. Less toxic and commercially available chemicals, such as tris(dimethylamino)arsine, have recently emerged as alternative As precursors. Nevertheless, InAs NCs made with such compounds need to be further optimized in terms of size distribution and optical properties in order to meet the standard reached with tristrimethylsilyl arsine. To this aim, in this work we investigated the role of ZnCl 2 used as an additive in the synthesis of InAs NCs with tris(dimethylamino)arsine and alane N,N-dimethylethylamine as the reducing agent. We discovered that ZnCl 2 helps not only to improve the size distribution of InAs NCs but also to passivate their surface acting as a Z-type ligand. The presence of ZnCl 2 on the surface of the NCs and the excess of Zn precursor used in the synthesis enable the subsequent in situ growth of a ZnSe shell, which is realized by simply adding the Se precursor to the crude reaction mixture. The resulting InAs@ZnSe core@shell NCs exhibit photoluminescence emission at ∼860 nm with a quantum yield as high as 42±4%, which is a record for such heterostructures, given the relatively high mismatch (6%) between InAs and ZnSe. Such bright emission was ascribed to the formation, under our peculiar reaction conditions, of an In−Zn−Se intermediate layer between the core and the shell, as indicated by X-ray photoelectron spectroscopy and elemental analyses, which helps to release the strain between the two materials.

Layer-by-layer assembly of CsPbX3 nanocrystals into large-scale homostructures

“…However, the greater removal of ligands will allow for more new ligands to attach to the NC surface, thus leading to a stronger increase in the PLQY. It is well known that CsPbX 3 is more ionic in nature compared to other types of NCs (i.e., II-IV and III-V NCs); 23,24 therefore, interactions between NCs and capping ligands have a more ionic nature as well and they are susceptible to be supplanted by polar solvents. Clearly, in the previously mentioned polarity range, this effect is minimized (Table 1).…”

“…17–19 MHP NCs show size- and composition dependent optical properties, 21 while their bandgap can be tuned from the blue to the near-infrared spectral region. 6 One of the main advantages of perovskite NCs is their facile synthesis procedure compared to II–IV 22 and III–V 23 NCs leading to near-unity photoluminescence quantum yield (PLQY) in solution. 24 Importantly, the performance of LEDs based on MHP NCs directly depends on the PLQY of the latter.…”

Near-Infrared Light-Emitting Diodes Based on RoHS-Compliant InAs/ZnSe Colloidal Quantum Dots

“…Yet, the integration of InAs QDs into optoelectronic devices such as NIR LEDs lags far behind the PbS-based ones. The main reasons for such limited advancement are the complex synthesis and poor optical properties of InAs QDs, along with limited material design and device engineering when using such material. , Electroluminescence (EL) from InAs QDs films has been demonstrated only very recently in QDs coated with multiple shells, a relatively elaborate architecture based on a In­(Zn)­As/​In­(Zn)­P/​GaP/ZnS system synthesized via pyrophoric and expensive tris­(trimethylsilyl)­phosphine and tris­(trimethylsilyl)­arsine precursors . The NIR-emitting LEDs fabricated using such QDs had an external quantum efficiency (EQE) of 4.6% at 850 nm.…”

“…In this work, we demonstrate a fully RoHS-compliant QD NIR LED operating at 947 nm based on InAs/ZnSe core/shell QDs. Key ingredients in our device are InAs/ZnSe QDs synthesized following our recently developed protocol 5 based on commercially available tris-dimethylamino arsine (amino-As), alane N,N -dimethylethylamine as reducing agent, and ZnCl 2 as additive. ZnCl 2 plays a double role: (i) it improves the size distribution of InAs QDs, acting as a Z-type ligand, and (ii) it enables the in situ overgrowth of a thin ZnSe shell on the InAs QDs, thanks to the formation of an In-Zn-Se interlayer at the interface (see Figure S1 for QDs characterization).…”

“…On the other hand, the flat band diagram suggests a small energy barrier of 0.4 eV for electrons at the TPBi/QD film interface. Yet, such energy barrier is due to the thin ZnSe shell, 5 whereas a favorable alignment between the lowest unoccupied molecular orbital of TPBi and the conduction band maximum of the InAs core is observed.…”