Low Cost and Strongly Adsorbed Melamine Formaldehyde Sponge Electrolyte for Nontraditional Quasi-Solid Dye-Sensitized Solar Cells

Currently, the high cost and the time-consuming preparation of electrolytes of quasi-solid-state dye-sensitized solar cells (QS-DSSCs) remain the key issue for the large-scale commercial fabrication of DSSCs. In this work, we propose a quasi-solid electrolyte based on a conductive melamine formaldehyde (MF) sponge scaffold for the fabrication of QS-DSSCs, which are MXene-MF, rGO-MF and PEDOT:PSS-MF. The three-dimensional porous structure in MF can quickly adsorb and store electrolytes, which shows high wettability, high organic solvent saturated adsorption capacity, and high electrical transmission performance. Specifically, the quasi-solid electrolyte prepared by this method can shorten the preparation method to less than 0.5 s, which also significantly reduces the preparation cost of the quasi-solid electrolyte. The QS-DSSC photoelectric conversion efficiency (PCE) of the melamine formaldehyde sponge can reach up to 7.822%. As compared with other conductive materials, MXene-MF is demonstrated to effectively improve the transmission performance of photogenerated electrons in the external circuit and the counter electrode interface. Meanwhile, the QS-DSSC based on MXene-MF has high catalytic activity, exchange current density, and IPCE. Specifically, the PCE reaches 26.92% under the indoor lighting condition of 1000 lux. Additionally, the QS-DSSC based on the composite sponge quasi-solid electrolyte exhibits excellent optoelectronic properties and long-term stability up to 90% in 1000 h. Finally, these QS-DSSCs based on the conductive MF sponge will have great promising potential in renewable energy applications such as flexible batteries and intelligent buildings.