Gel electrolyte materials formed from a series of novel low molecular mass organogelators for stable quasi-solid-state dye-sensitized solar cells
Electrolyte materials are the key components in dye-sensitized solar cells (DSCs) and are very crucial to the performance and long-term stability of DSCs. We developed a series of diamide derivatives as novel low molecular mass organogelators (LMOGs) for DSCs. These LMOGs contain different numbers (2, 6, 5 and 9) of methylene groups (-CH2-) between the two amide carbonyl groups and exhibit distinctive self-assembly behaviors. The gel electrolytes prepared by these LMOGs possess high gel-to-solution transition temperatures (over 100 degrees C) and the stability of DSCs is largely enhanced. More importantly, the parity of the number of -CH2- and their special molecular arrangements have a remarkable influence on the self-assembly of the gelators resulting in a significantly different morphology, and further influence the photovoltaic performances of DSCs. It is found that the LMOGs containing odd-numbered -CH2- lead to a much better charge transport of the gel electrolytes, inducing a longer electron lifetime and higher incident photon-to-electron conversion efficiency compared with the LMOGs containing even-numbered -CH2-. Finally, a superior quasi-solid-state DSC based on the gelator containing five -CH2- is obtained, which exhibits a photoelectric conversion efficiency of 7.53% and excellent thermal and light-soaking stabilities during accelerated aging tests.