title: Electrochemical Charging of CdSe Quantum Dots: Effects of Adsorption versus Intercalation.
abstract: Effects of electrochemical charging of quantum dots (QDs) have been reported previously, wherein optical and electrical properties could be modulated through cation adsorption and electron injection into the quantum-confined 1Sestates. In this work, we report two different modes of electrochemical double-layer charging in CdSe QDs and their effects on the electronic and optical properties. We show that the charging mechanism at the interface involves cation intercalation for smaller ions, such as Li+, Na+, or K+, and cation adsorption for larger bulky ions, such as tetrabutylammonium ions, where steric hindrance precludes intercalation. As a result, while cation adsorption leads to an increase in the absorbance in the mid-infrared spectral range, cation intercalation into the CdSe core results in an absorbance increase from the visible to infrared spectral range, an enhancement in radiative lifetime of e-, an increase of 158% in the intensity of band-edge photoluminescence, and strong emission in the near-infrared spectral range as a result of the formation of Se vacancies. The nature of charging mechanisms is discussed using the results of combined photoluminescence, radiative lifetime, and X-ray photoemission studies. The cation-coupled electronic and optical modulation reported here in CdSe QDs have important implications for electrochromic smart windows, photovoltaics, and other devices.
authors.affiliation: Howard P. Isermann Department of Chemical and Biological Engineering and ‡Department of Physics, Applied Physics & Astronomy, Rensselaer Polytechnic Institute , Troy, New York 12180, United States.
authors.forename: Ajinkya
authors.initials: A
authors.lastname: Puntambekar
authors.affiliation: Howard P. Isermann Department of Chemical and Biological Engineering and ‡Department of Physics, Applied Physics & Astronomy, Rensselaer Polytechnic Institute , Troy, New York 12180, United States.
authors.forename: Qi
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Howard P. Isermann Department of Chemical and Biological Engineering and ‡Department of Physics, Applied Physics & Astronomy, Rensselaer Polytechnic Institute , Troy, New York 12180, United States.
authors.forename: Lauren
authors.initials: L
authors.lastname: Miller
authors.affiliation: Howard P. Isermann Department of Chemical and Biological Engineering and ‡Department of Physics, Applied Physics & Astronomy, Rensselaer Polytechnic Institute , Troy, New York 12180, United States.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Smieszek
authors.affiliation: Howard P. Isermann Department of Chemical and Biological Engineering and ‡Department of Physics, Applied Physics & Astronomy, Rensselaer Polytechnic Institute , Troy, New York 12180, United States.
authors.forename: Vidhya
authors.identifier: 0000-0003-2682-3833
authors.initials: V
authors.lastname: Chakrapani
keywords: adsorption; electrochemical charging; electrochromism; intercalation; lifetime; quantum dots