Effects of carbon dots on ZnO nanoparticle-based dye-sensitized solar cells

Abstract

ZnO nanoparticles have been assessed the effects of added carbon dots (Cdots) on the performance of photovoltaic devices: ZnO(100) and ZnO(20) with particle sizes of 94 and 20 nm, respectively, were hybridized with Cdots and characterized by current–voltage measurements under the illumination condition. The photovoltaic conversion of dye-sensitized solar cells (DSSCs) was effective for ZnO(20) superior to Zn (100) and for the incorporation of 10 wt% Cdots in the hybrid nanostructures. Moreover, when the mole ratio (ethylenediamine:citric acid) between raw materials of Cdots was 2:1, the conversion efficiency was highest (5.9%), and this value was 7 times higher than that of ZnO(20) DSSC without Cdots. Electrochemical impedance spectroscopy also showed that the charge transfer resistance property was lowest for Cdots(2:1)-hybridized ZnO(20) DSSC. It can be thus concluded that the performance of ZnO-based DSSCs is improved by the size-minimization of ZnO and the addition of adequate amount of Cdots. The effect of carbon dots was discussed based on electron transfer between ZnO and Cdots under the illumination.