Trap Passivation in Indium-Based Quantum Dots through Surface Fluorination: Mechanism and Applications

Abstract

Treatment of InP colloidal quantum dots (QDs) with hydrofluoric acid (HF) has been an effective method to improve their photoluminescence quantum yield (PLQY) without growing a shell. Previous work has shown that this can occur through the dissolution of the fluorinated phosphorus and subsequent passivation of indium on the reconstructed surface by excess ligands. In this article, we demonstrate that very significant luminescence enhancements occur at lower HF exposure though a different mechanism. At lower exposure to HF, the main role of the fluoride ions is to directly passivate the surface indium dangling bonds in the form of atomic ligands. The PLQY enhancement in this case is accompanied by red shifts of the emission and absorption peaks rather than blue shifts caused by etching as seen at higher exposures. Density functional theory shows that the surface fluorination is thermodynamically preferred and that the observed spectral characteristics might be due to greater exciton delocalization over the outermost surface layer of the InP QDs as well as alteration of the optical oscillator strength by the highly electronegative fluoride layer. Passivation of surface indium with fluorides can be applied to other indium-based QDs. PLQY of InAs QDs could also be increased by an order of magnitude via fluorination. We fabricated fluorinated InAs QDbased electrical devices exhibiting improved switching and higher mobility than those of 1,2-ethanedithiol cross-linked QD devices. The effective surface passivation eliminates persistent photoconductivity usually found in InAs QD-based solid films.

Surface passivation extends single and biexciton lifetimes of InP quantum dots

“…22 On the other hand, our result is not consistent with other reports that suggest that HF treatment removes electron traps on InP QDs by the passivation of surface indium dangling bonds. 22,23 Exciton dynamics in InP@ZnS core@shell QDs: passivation of both electron and hole traps…”

“…[20][21][22][23][24][25][26] The rst passivation method employed a post-synthetic HF treatment of InP QDs under illumination. [20][21][22][23]25 The HF treatment has been suggested to remove the surface P dangling bonds through a photochemical reaction of trapped holes with the P atom, which is then attacked by the F À ions and eventually detach from the InP surface. 25 Meanwhile, a recent study suggested an alternative/complementary mechanism where the F À treatment may act through removing the electron traps caused by the surface indium dangling bonds.…”

Plasmonic Hot‐Electron‐Induced Control of Emission Intensity and Dynamics of Visible and Infrared Semiconductor Quantum Dots

“…This can create a situation where in the presence of Al oxide allows the electrons in the cores to be transferred to the ligands or causes partial leakage of electron wavefunctions. [ 39–41 ]…”

Модификация Атомной И Электронной Структуры Поверхности Полупроводников А-=sup=-Iii-=/Sup=-В-=sup=-v-=/Sup=- На Границе С Растворами Электролитов О Б З Ор

“…Квантовые точки бывают двух типов: коллоидные [299,300] и эпитаксиальные [301,302]. Для пассивации коллоидных квантовых точек InP и InAs, формируемых в растворах оксида триоктилфосфина, используется, как правило, травление растворами HF или NH 4 F [299,303,304]. Такая обработка приводит к фотохимическому удалению оборванных связей поверхностных атомов фосфора (мышьяка) и к последующей пассивации поверхностных атомов индия лигандами оксида триоктилфосфина [305].…”