Improved optical, electrochemical and photovoltaic properties of dye-sensitized solar cell composed of rare earth-doped zinc oxide.

The double composite layer composed of europium and terbium doped zinc oxide (Eu³⁺,Tb³⁺@ZnO) as downconversion material (DC) and neodymium and ytterbium-doped zinc oxide (Nd³⁺,Yb³⁺@ZnO) as upconversion materials (UC) was prepared and used as photoanodes to achieve the higher photovoltaic efficiency of dye sensitized solar cell(DSSCs). The double composite layer FTO/Eu³ + ,Tb³⁺@ZnO/TiO₂/ Nd³⁺,Yb³⁺@ZnO have two disparate units; one provide downconversion luminescence by Ultraviolet excitation assigned to ⁷F₀-⁵L₆ of Eu³⁺, ⁷D₄-⁷F₅, of Tb³⁺, ⁵D₄-⁷F₄ of Tb³⁺, ⁷F₀-⁵D₁ of Eu³⁺ and other gives upconversion luminescence (λ_ex = 980 nm) attributed to ⁴F_7/2-⁴I_15/2, ²H_11/2-⁴I_15/2,⁴S_3/2-⁴I_15/2,⁴F_9/2-⁴I_15/2. The photoelectric efficiency of double composite layer device E (FTO/Eu³⁺,Tb³⁺@ZnO/TiO₂/Nd³⁺,Yb³⁺@ZnO) attains 2.68%, notably higher than device with undoped zinc oxide (ZnO). Higher efficiency in device E was due to enhancement of the light harvesting achieved by down converters and upconverters by converting Ultraviolet (UV) and near infrared (NIR) radiations to visible emission respectively. Furthermore, Eu³⁺,Tb³⁺@ZnO acts as confinement layer which suppresses the dark current and also inhibits the charge recombination. [ABSTRACT FROM AUTHOR]