Synthesis and Characterization of Gallium-Doped CdSe Quantum Dots

Abstract

Developing electronic doping of colloidal quantum dots is important for basic science and technology. In this article, the doping of colloidal CdSe quantum dots with gallium atoms is reported. Gallium doping of CdSe quantum dots produces important changes in electronic and optical properties of the material. The gallium doping shows a significant impact on the growth kinetics of quantum dots, which reveals important clues about the mechanism of the gallium dopant incorporation into the CdSe. The results show that the gallium doping significantly impacts the conductivity of CdSe thin film made of the quantum dots as well as the photoluminescence and chemical reactivity of the quantum dots, in agreement with the expected ntype character.

Strategies for the Controlled Electronic Doping of Colloidal Quantum Dot Solids

“…For the case of Al doping, thin‐film transistor (TFT) measurements confirmed that it promotes n‐type doping of the CQDs, raises the Fermi level, and increases carrier mobility values from 0.2 to 0.9 cm 2 V −1 s −1 . Ga doping has also been shown to raise the Fermi level of CdSe CQDs and increase n‐type conductivity, as well as enhance the chemical reactivity of the dots, due to the electron‐donating character of the dopant . Regarding In doping in CdSe CQDs, Choi et al.…”

“…Also, remote doping of CQDs has received significant attention as a means to study optoelectronic effects due to heavy charging of the CQDs without altering their structure. Nevertheless, heavy charging of CQDs may initiate charge compensation processes, for example the ability of certain CQD materials to be negatively charged by an excess of electrons in the conduction band may be limited by the transfer of the excess free electrons to the surface of the dots and their subsequent consumption in permanent electrochemical reactions . Such an effect will depend on the electron energy, as determined by both the CQD material and the degree of quantum confinement, and can explain why certain materials such as nanocrystalline ZnO can maintain electrons in their conduction band for longer periods of time than others such as CdSe CQDs …”

Gallium‐Induced Perturbation of Zinc Selenide Quantum Dots Electronics

“…In gallium sesquiselenide, Ga 2 Se 3 , for example, there exists nine electrons per gallium‐selenium pair, resulting in a valence mismatch semiconductor system that crystallizes in a defected zinc blende structure, where a third of the gallium sites are vacant. These vacancies are important sources of the desired structural, optical and electronic properties of the semiconductor crystals . Semiconductors whose elements exhibit valence matching can be modulated to exhibit structural vacancies by introducing impurities through doping or alloying .…”

“…A Fermi level, equivalent to the band edge of the quantum dot causes an electron transfer between the quantum dot and the electrode, generating current. The peak current thus corresponds to the band energy of either the conduction or valence band and the peak separation is a measure of the band gap energy and as such the study of the electrochemistry of quantum dots can reveal information regarding various electronic transitions and possible decomposition events during oxidation or reduction . Since the energy levels of surface traps of quantum dots are difficult to predict, it is important to establish the correlation between the electrochemical and optical band gaps.…”

“…These vacancies are important sources of the desired structural, optical and electronic properties of the semiconductor crystals. [4] Semiconductors whose elements exhibit valence matching can be modulated to exhibit structural vacancies by introducing impurities through doping or alloying. [5] Introduction of chemical impurities (doping) can result in vacancy generation as the crystal seeks equilibrium between local charge balance, bonding coordination and valence around the impurity while thermal energy can create vacancies even in ultrapure materials at temperatures above absolute zero.…”