Porphyrin-sensitized quasi-solid solar cells with MOF composited titania aerogel photoanodes

ZnTPP-COOH porphyrin-based quasi-solid dye-sensitized solar cells were fabricated with the following three different photoanode materials: Ni-MOF@titania aerogel composite, Cu-MOF@titania aerogel composite, and pure titania aerogel. Their photovoltaic performances were investigated through photocurrent-photovoltage (J-V) curve, electrochemical impedance spectroscopy (EIS), intensity modulated photocurrent spectroscopy, and transient measurements of photocurrent and photovoltage decay. Among the three cells, the enhancement of photocurrent is observed in cells containing NiMOF@titania aerogel photoanodes. As a result, the Ni-MOF@titania aerogel photoanode-based cell achieved the highest photocurrent density of 8.88 mA/cm(2) and power conversion efficiency of 2.34%. This value is higher than that of the other two devices. Moreover, the EIS analysis is used to understand better the possible electron transfer behind the photocurrent boosting in Ni-MOF@titania aerogel photoanode-based cell. Low Rct value (44.1 Omega) and low Td value of the Ni-MOF@titania aerogel device are the key factors to improve the electron flow, the Warburg diffusion of electrolyte, as well as the regeneration process. These factors are attributed as the reason for their best performance among other devices. Based on the results obtained, the plausible mechanism for electron transfer is discussed using the energy level cascades of TiO2/MOF/porphyrin dye. The transient measurements indicated that the devices exhibited good reproducibility under multiple illuminations. (C) 2020 Elsevier Ltd. All rights reserved.