This study investigates the treatment effects of ZnO and Al:ZnO (AZO) photoanodes on short-circuit photocurrent (J(sc)) and open-circuit photovoltage (V-oc) of quantum dot sensitized solar cell using Ag nanoparticles (Ag NPs). Current density-voltage (J-V) characterization showed that J(sc) of QDSSC rises for treated ZnO photoanode with Ag NPs, whereas it decreases in AZO/Ag NPs photoanode based QDSSCs. Also, it was found that Voc raises when treating both ZnO and AZO photoanodes of QDSSCs with Ag NPs. These results were studied using electrochemical impedance spectroscopy (EIS) and absorption spectra. EIS results indicated that recombination resistance of photoanode/electrolyte interfaces of QDSSC increases with decoration of Ag NPs on ZnO and AZO photoanodes which, consequently, results in reduction of electron back into electrolyte. Furthermore, it was observed that chemical capacitance of photoanode enhances with treatment of ZnO photoanode, while being extremely reduced for AZO photoanode. (C) 2015 Elsevier Ltd. All rights reserved.