Efficiency Improvement of Dye-sensitized Solar Cells by In-situ Fluorescence Resonance Energy Transfer
A 1,8-naphthalimide derivative (H-NIM), with an alkyl carboxylic chain, is rationally designed and synthesized for efficient utilization of fluorescence resonance energy transfer (FRET) in dye-sensitized solar cells (DSSCs). The H-NIM fluorophores, which can absorb the ultraviolet light and emit green light under illumination, are doped into a TiO2 mesoporous film with N719 molecules by a co-adsorption method. The H-NIM fluorophores adsorb on the TiO2 surface as N719 does with their carboxylic groups, ensuring more efficient energy transfer from H-NIM (FRET donor) to N719 (FRET acceptor) via in-situ FRET and thereby promoting light harvesting of N719 molecules in the spectral range of ultraviolet light. The co-adsorption of H-NIM and N719 also reduces the charge recombination by shielding the contact area between TiO2 and electrolyte. Our results show that the optimal doping ratio of H-NIM fluorophore is 17 %, at which the power conversion efficiency (PCE) of DSSCs is improved by 10.8 % and 21 % under one sun (AM1.5G) and T5 fluorescent lamps of 600 lux illumination, respectively, as compared with that only adsorbing N719 molecules.