Bismuth sulfide sensitized TiO2 arrays for photovoltaic applications

We report the use of chemically deposited bismuth sulfide (Bi2S3) for sensitization of TiO2 nanotube arrays (TNA) obtained by electrochemical anodization. Deposition of Bi2S3 onto TNA was carried at 25 °C for 20 min, 1 h and 3 h, showing structural changes and different Bi/S ratio at shorter deposition time. The best photocurrent and external quantum efficiency was obtained at 1 h. Electrochemical impedance measurements were correlated with the structural, optical, and electronic properties of the sensitized arrays, finding a decisive role of the recombination resistance and chemical capacitance in determining the photoelectrochemical behavior. A three-order of magnitude difference in electron life time (τn) was found in sensitized arrays with different Bi/S ratio, suggestive of the separation of the limiting phenomena inside the oxide (τn = ms) and chalcogenide (τn = s) films.