Enhanced sunlight harvesting of dye-sensitized solar cells through the insertion of a (Sr, Ba, Eu)2SiO4-TiO2 composite layer

• The efficiency of DSSCs are improves with an insertion DC-TiO2 composite layer.
• DC phosphor shifts violet-blue light into the main absorption range of N719 dye.
• The energy of DC phosphor is transferred to the dye via the FRET processes.

TiO2 nanoparticle-based dye-sensitized solar cells (DSSCs) were modified by inserting a composite layer of (Sr, Ba, Eu)2SiO4-TiO2 on top or at bottom of the transparent layer, so as to enhance their sunlight harvesting capability. Due to the presence of the (Sr, Ba, Eu)2SiO4 phosphor layer, absorption band of the photoanodes was shifted from violet region to the active photoabsorption region of the dye N719 used in the DSSCs. Power conversion efficiency of the devices showed that the introduction of such phosphor significantly enhanced light harvesting capability of the DSSCs. The electrons which are produced by the (Sr, Ba, Eu)2SiO4 particles, reduced I3− to I−, so that the concentration of I3− was at a lower level in the electrolyte. As a result, the number of electrons injected into the TiO2 conduction band (CB) by I3− ions was decreased. Under one sun illumination (AM 1.5 G, 100 mW cm−2), the devices with the insertion of the (Sr, Ba, Eu)2SiO4-TiO2 composite layer showed an optimal power conversion efficiency of 5.97%, which was increased by 23.34% as compared with that (4.84%) of the devices without the composite layer. The introduction of down-conversion phosphors into DSSCs is an effective approach to improve their performances.

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