Regulation of energy levels and kinetics in dye-sensitized solar cells: Synergistic effect of N,N-bis(9,9-dimethyl-fluoren-2-yl)-aniline and 3,4-ethylenedioxythiophene

Three D-π-A type organic dyes are used to demonstrate synergistic effect of 3,4-ethylenedioxythiophene (EDOT) and N,N-bis(9,9-dimethyl-fluoren-2-yl)-aniline (DFA) on performance of device in iodine and cobalt electrolytes. The integrative analysis of the incident photon-to-collected electron conversion efficiency (IPCE), the time-correlated single-photon counting (TCSPC) and transient absorption spectra disclose that the rich-electron EDOT effectively improves short-circuit current densities by achieving a broad spectra response from a molecular engineering viewpoint. Electrical impedance and current-voltage simulation reveal that DFA as an interface engineering block is able to enhance open-circuit voltage mainly by simultaneous decreasing the thermodynamics and kinetics loss. The quantitative analysis of energy loss shows that the cobalt electrolyte is suitable for highly efficient cell because of their relatively low free energy loss of regeneration process and low energy loss caused by light-intensity-dependent recombination.