Enhanced performance of dye sensitized solar cells by using a reduced graphene oxide/TiO2 blocking layer in the photoanode

A reduced graphene oxide/TiO2 (RGO/TiO2) blocking layer in the photoanode of a dye sensitized solar cell (DSSC) was fabricated in a simple way by depositing a RGO/TiO2 paste onto a FTO substrate through screen printing method. The RGO content in the RGO/TiO2 blocking layer was optimized for better DSSC performance. The effect of the RGO/TiO2 blocking layer on the performance of the DSSC was examined based on the electrochemical impedance spectral analysis, the photocurrent-voltage measurement, and the open-circuit voltage decay technology. After the introduction of RGO/TiO2 blocking layer in the photoanode, direct contact between the electrolyte and the FTO glass surface was prevented. The electron transfer from the TiO2 film to the FTO glass substrate was thus improved, the charge recombination rate suppressed, the electron transport rate enhanced, and the electron collection efficiency increased, resulting in higher current density. At the best level of RGO in the composite blocking layer, the DSSC has an energy conversion efficiency (eta) of 7.48% with a J(sc) of 15.29 mA cm(-2), a V-oc of 0.74V and a FF of 0.66, indicating a 29% and a 30% increase in J(sc) and eta, respectively, compared to that of a DSSC based on pure TiO2 photoanode, which exhibits a eta value of 5.76% with a J(sc) of 11.85 mA cm(-2), a V-oc of 0.74 V, and a FF of 0.66. The introduction of the RGO/TiO2 blocking layer in the photoanode could really enhance the efficiency of DSSC by preventing the direct contact between the electrolyte and the FTO glass surface. (C) 2017 Elsevier B.V. All rights reserved.