Efficient triple-layer photoanode incorporated with nitrogen-doped TiO₂ nanocrystals for CdS quantum dot-sensitized solar cells

Abstract

Nitrogen-doped (N-doped) TiO2 nanocrystals were synthesized by adopting a wet chemical method, in which titanium tetraisopropoxide (TTIP) was hydrolyzed with aqueous ammonia under a continuous flow of nitrogen gas. Triple layer photoanode, consisting of TiO2 P90, TiO2 P25 and N-doped TiO2 nanomaterials, was developed by utilizing the spin coating and doctor blading techniques and subjecting to thermal treatment. Photoanodes were sensitized with CdS quantum dots by the successive ionic layer adsorption and reaction method. Quantum dot-sensitized solar cells (QDSSCs) were fabricated by assembling photoanodes with Pt counter electrode and polysulfide electrolyte. Material characterizations for N-doped TiO2 were conducted by TEM, XRD, UV-Visible spectroscopy and Mott-Schottky techniques. Fabricated QDSSCs were evaluated by incident photon-to-electron conversion efficiency (IPCE) spectroscopy, current-voltage (J-V) characteristics and electrochemical impedance spectroscopic (EIS) measurements. QDSSCs with N-doped TiO2 achieved an overall power conversion efficiency of 1.35 % while QDSSCs with TiO2 P25 showed only 1.04 %. Overall power conversion efficiency enhancement of 29.81 % was achieved by incorporating N-doped TiO2 in the triple-layer photoanode, which Is attributed to increased photocurrent generation in the photoanode. Enhanced IPCE and reduced charge transfer resistance at the photoanode/ electrolyte interface (R2 ct) agree with improved photoactivity of the triple-layer photoanode incorporated with N-doped TiO2. Show more