Solid-state dye-sensitized solar cells based on ZnO nanocrystals

Abstract

We report on the development of solution-processed ZnO-based dye-sensitizedsolar cells. We fabricate mesoporous ZnO electrodes from sol–gel processednanoparticles, which are subsequently sensitized with conventional rutheniumcomplexes and infiltrated with the solid-state hole transporter medium2, 2′, 7, 7′-tetrakis-(N, N-di-p-methoxyphenylamine)-9, 9′-spirobifluorene (spiro-OMeTAD). Starting from ZnO nanorods synthesized from solution,we investigate the porous ZnO film morphology using various precursor formulations. Thenature of the polymeric additive used in the initial ZnO formulation, as well as the ZnOelectrode sintering treatment, is varied and its influence on device performance andcharge dynamics, probed by transient perturbation techniques, is discussed. Weshow that using ethyl-cellulose in the initial ZnO formulation is responsible for animproved dye loading on the ZnO porous electrode, while a gradual sintering step at350 °C is suitable for the proper removal of the organic phases that can be found in the ZnO filmsafter their deposition by spin-coating. Using only 800 nm thick porous ZnO electrodessensitized by N719, the best performing device exhibits a short-circuit current density of2.43 mA cm − 2 under simulatedsolar emission of (100 mW cm − 2), associated with an overall power conversion efficiency of 0.50%.