Highly luminescent InP–In(Zn)P/ZnSe/ZnS core/shell/shell colloidal quantum dots with tunable emissions synthesized based on growth-doping

Abstract

InP quantum dots (QDs) are considered as the most promising alternative to Cd-based QDs with the lower toxicity and emission spectrum tunability ranging from visible to near-infrared region. Although high-quality...

Fully Printed Optoelectronic Synaptic Transistors Based on Quantum Dot–Metal Oxide Semiconductor Heterojunctions

“…The results show that the annealed film of InP/ZnSe QDs exhibited diffraction peaks at 26.5°, 44.2°, and 51.8°c orresponding to the (111), (220), and (311) planes, respectively, and no characteristic peak of the SnO 2 film could be observed. 36,37 The film thicknesses of the printed InP/ZnSe QDs and SnO 2 films were ∼40 and ∼12 nm, respectively, as confirmed in the height profile by atomic force microscopy (AFM), as shown in Figure 1g. Further, the AFM and scanning electron microscope (SEM) results show that the surface topography of the printed InP/ZnSe QDs and SnO 2 films were relatively smooth and had no holes, and the rootmean-square (RMS) roughness values were 0.25 and 2.38 nm for SnO 2 and InP/ZnSe QDs films, respectively (Figure S3).…”

“…While InP QDs dispersed in solution displayed an excitonic peak at ∼522 nm, the annealed InP QD film shows no obvious excitonic peak in the absorption spectrum (Figure S1b), which is inferred to be a result of oxidation during printing and annealing, because the InP QDs without a protective shell are unstable. The corresponding XPS spectra in Figure S2 show a small peak of the binding energy in the range of 127–130 eV and a strong peak of the binding energy close to 134 eV, which are associated with P 3– for InP and P 3+ and P 5+ for InPO x , respectively, confirming that most of the InP QDs were oxidized. , Meanwhile, the shell growth of ZnSe on InP QDs induced a red shift of the excitonic peak to ∼532 nm (∼2.2 eV), an indication of partial delocalization of photogenerated charge carriers in the shell of ZnSe. The slightly decreased optical band gap of InP/ZnSe QDs made these QDs available for implementation in human visual neural networks.…”

“…The corresponding XPS spectra in Figure S2 show a small peak of the binding energy in the range of 127−130 eV and a strong peak of the binding energy close to 134 eV, which are associated with P 3− for InP and P 3+ and P 5+ for InPO x , respectively, confirming that most of the InP QDs were oxidized. 36,37 Meanwhile, the shell growth of ZnSe on InP QDs induced a red shift of the excitonic peak to ∼532 nm (∼2.2 eV), an indication of partial delocalization of photogenerated charge carriers in the shell of ZnSe. The slightly decreased optical band gap of InP/ZnSe QDs made these QDs available for implementation in human visual neural networks.…”

Blue-Emitting InP/GaP/ZnS Quantum Dots with Enhanced Stability by Siloxane Capping: Implication for Electroluminescent Devices

“…InP QDs with low toxicity are regarded as an ideal alternative to Cd-based QDs due to their suitable and similar luminescence range . Despite the development of InP QDs being inferior to that of Cd-based QDs, recent significant advances in the synthesis of InP QDs make it possible for them to compete with Cd-based QDs. − The corresponding record PL QY for InP QDs with red and green emission has been pushed up to near-unity. Nevertheless, in contrast to red- and green-emitting QDs, synthesis of high-quality and blue-emitting InP QDs still faces challenges. − At first, typical blue-emitting InP core sizes are below 2 nm, and thus the precise size control is particularly difficult.…”

“…In an earlier study, wide-band gap ZnS epitaxy directly on the InP core was implemented, − but the lattice mismatch of InP-ZnS resulted in the unexpected interface defects, which prevented the formation of a perfect heteroepitaxial interface without defects and limited the thickness of an epitaxial shell. Most recently, an intermediate buffer layer with a lattice constant close to those of InP and ZnS (e.g., ZnSe, ,,, ZnSeS, − and GaP ,, ) has been used to reduce lattice mismatch between the core and shell. Because the ZnSe shell inevitably causes large red shift of emission, the GaP intermediate shell is widely used in blue-emitting InP QDs.…”