4‐1: Invited Paper: Role of Phosphorus Oxidation in Controlling the Luminescent Properties of Indium Phosphide Quantum Dots

Abstract

Indium phosphide (InP) is the leading Cd-free quantum dot material for application in photoluminescence downconversion display and lighting technologies. To date the performance of InP quantum dots (QDs) has lagged behind cadmium selenide in terms of both luminescence line width and quantum yield. Extensive studies in our lab have implicated kinetically persistent magic-sized cluster intermediates as a leading contributor to polydispersity in these samples, providing new opportunities for achieving high color purity. Now, using a combination of solid-state NMR spectroscopy and recently developed benchtop X-ray emission spectroscopy, we have studied the evolution of oxidized phosphorus species during both synthesis and shell growth.

Probing Sulfur Chemical and Electronic Structure with Experimental Observation and Quantitative Theoretical Prediction of Kα and Valence-to-Core Kβ X-ray Emission Spectroscopy

“…The design allows efficient use of a large spot size, which serves to increase the efficiency when operating with a conventional unfocused laboratory X-ray tube and decreases the damage done to radiation-sensitive samples. These capabilities have already been demonstrated and utilized in a recent study on the speciation of sulfur in biochars and for the problem of the speciation and local electronic structure of phosphorus in InP quantum dots. , These studies demonstrate synchrotron-quality energy resolution in often-comparable measurement times. In addition, for the narrow problem of determination of the P oxidation state, lab-based XES agreed with results from 31 P magic-angle spinning NMR but required much shorter measurement time and far less sample mass …”

“…Core-hole generation rates for samples illuminated by suitably chosen conventional X-ray tubes are often quite comparable to those for monochromatic illumination at third-generation insertion device beamlines. The modest, but growing, rebirth of laboratory-based X-ray absorption and emission spectroscopies has included recent development and application of a particularly simple XES spectrometer for sulfur and other nearby light elements. ,,, Given that it is now technically feasible that sulfur XES could become a high-access method, it becomes important to more fully explore the actual chemical and electronic sensitivities of sulfur XES, from both an experimental and theoretical perspective.…”

“…The modest, but growing, rebirth of laboratory-based X-ray absorption and emission spectroscopies has included recent development and application of a particularly simple XES spectrometer for sulfur and other nearby light elements. 21,33,35,36 Given that it is now technically feasible that sulfur XES could become a high-access method, it becomes important to more fully explore the actual chemical and electronic sensitivities of sulfur XES, from both an experimental and theoretical perspective. Hence, in the present work, a comprehensive set of experimental results for S Kα and Kβ XES, collected from extensive prior work in the literature and augmented with new measurements, are compared to theoretical calculations using linear-response time-dependent density functional theory (LR-TDDFT).…”

Vacuum formed temporary spherically and toroidally bent crystal analyzers for x-ray absorption and x-ray emission spectroscopy

“…This is an updated version 37 of an earlier camera 38 that has seen good use in a lower-energy XES instrument. [39][40][41][42] The camera has a 3.2 × 5.6 mm 2 field of view. It was mounted on a micrometer-driven vertical translation stage and manually repositioned to achieve mosaic coverage of the x-ray intensity's spatial distribution.…”

High efficiency heavy metal free QD‐LEDs for next generation displays

“…Improvements have been reported with new shell compositions such as ZnSeS alloys, ZnSe, or GaP, which enable thicker shells by alleviating lattice strain. Additionally, facile oxidation of the surface of the InP core results in interfacial defects and lower luminescence efficiency . The presence of electronic trap states associated with the structural defects are also responsible for the wider emission spectra …”