Systematic study of mono- and tri-TEMPO-based electrolytes for highly efficient next-generation dye-sensitised photo harvesting

In the present work, we design and synthesized of TEMPO(TEMPO-I = 2((2,2,6,6-tetramethy1-1-(l1-oxidanyl) piperidin-4-yl)oxy)ethan-1-amine and TEMPO-III = tris(2((2,2,6,6-tetramethy1-1-(l1-oxidanyl)piperidin-4-yl) oxy)ethyl)amine)-based redox couple electrolytes and used in the application of dye-sensitised solar cells (DSSCs). After preparation, the TEMPO-based redox couples are characterised by thermogravimetric analysis (TGA), cyclic voltammetry (CV) and impedance spectroscopy (EIS) techniques. The conventional electrolyte BIMI (1-butyl-3-methyl imidazolium iodide) was incorporated into the TEMPO redox couple, and a comparative study was performed. Such type TEMPO-III/BIMI hybrid redox couple displayed the highest photo-current density (J(sc)) and enhanced photo-voltage (V-oc) and an efficiency (eta = 5.12%) upon 1 sun light illumination. EIS was performed to investigate the inter-kinetic and recombination dynamics of the fabricated devices. The best performing devices underwent long-term stability verification.