Surface ion transfer growth of ternary CdS1−xSex quantum dots and their electron transport modulation

Abstract

We report a surface ion transfer method to synthesise ternary alloy CdS_1−xSe_x (0 ≤ x ≤ 1) quantum dots (QDs) in situ on TiO₂ nanoparticles. By tuning the content of selenium in such quantum dots, the optical absorption spectra can be controllably widened to cover the most of the visible light range. The electron transport of such QDs can be modulated by changing the interfacial electronic energy between CdS_1−xSe_x QDs and TiO₂ nanoparticles. The QDs with optimized selenium content (x = 0.72) give a balance between a broad optical absorption and a suitable energy band alignment. The homogenous alloy CdS_1−xSe_x QDs achieve a maximum light-harvesting efficiency over 90%, and generate a photocurrent density larger than 10 mA cm⁻², which is 2.6- and 1.4-times that of binary CdS and CdSe QDs sensitized photovoltaic devices.