(718f) Electrochemical Charging of CdSe Quantum Dots: Effects of Adsorption Versus Intercalation

Effects of electrochemical charging of quantum dots have been reported previously, wherein optical and electrical properties could be modulated through cation adsorption and electron injection into the quantum-confined 1S_e states. In this presentation, we report two different modes of electrochemical double layer charging in CdSe quantum dots 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 increase in the absorbance in the mid-infrared spectral range, cation intercalation into CdSe core results in an absorbance increase from 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, photovoltaic and other devices.