Surface ion transfer growth of ternary CdS1−xSex quantum dots and their electron transport modulation†
We report a surface ion transfer method to synthesise ternary alloy CdS1−xSex (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 CdS1−xSex 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 CdS1−xSex 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.