Conformal growth of anodic nanotubes for dye-sensitized solar cells : part I. planar electrode

Abstract

In this review, we dissect nanotube growth under a systematic changing of electrode configurations and analyze relevant solar cell constructions as well as performances, in an attempt to explore efficient approaches to harvest solar energy. It is divided into two parts for discussion: planar and nonplanar electrodes, as a conformal coating of anodic nanotubes can be formed on an electrode regardless of its geometric shape. The first part is presented in this paper. To date, the most efficient dye-sensitized solar cells (DSCs) based on anodic nanotubes exhibit a power conversion efficiency of 7∼8%, whereas those based on nanoparticles show a higher efficiency of 11∼12%. This is due to a lower surface area per photoanode volume for nanotubes with respect to nanoparticles. It is calculated that, for a given photoanode volume, it requires the nanotube diameter to go down to ∼30 nm to generate a comparable surface area with nanoparticles of ∼20 nm. For single-sided tube growth, three dominant fabrication routes render two major cell configurations: backside and frontside illuminations. The relevant cell structures and performances are discussed and compared. For double-sided tube growth, a parallel DSC is constructed for doubled surface area and power output.