Improved performance of dye-sensitized solar cells using dual-function TiO2 nanowire photoelectrode

Abstract

A unique, hierarchically structured, aggregated TiO2 nanowire (A-TiO2-nw) is prepared by solvothermal synthesis and used as a dual-functioning photoelectrode in dye-sensitized solar cells (DSSCs). The A-TiO2-nw shows improved light scattering compared to conventional TiO2 nanoparticles (TiO2-np) and dramatically enhanced dye adsorption compared to conventional scattering particles (CSP). The A-TiO2-nw is used as a scattering layer for bilayer photoelectrodes (TiO2-np/A-TiO2-nw) in DSSCs to compare the cell performance to that of devices using state-of-the-art photoelectrode architectures (TiO2-np/CSP). The DSSCs fabricated using bilayers of TiO2-np/A-TiO2-nw show improved power conversion efficiency (9.1%) and current density (14.88 mA cm(-2)) compared to those using single-layer TiO2-np (7.6% and 11.84 mA cm(-2)) or TiO2-np/CSP bilayer structures (8.7% and 13.81 mA cm(-2)). The unique contribution of the A-TiO2-nw layers to the device performance is confirmed by studying the incident photon-to-current efficiency. The enhanced external quantum efficiencies at approximately 520 nm and 650 nm clearly reveal the dual functionality of A-TiO2-nw. These unique properties of A-TiO2-nw may be applied in other devices utilizing light-scattering n-type semiconductor.