Electro-deposition under a modulated electrical field as an enhanced method for the preparation of an efficient photoanode of dye-sensitized solar cells

Abstract

This paper describes an application of a new electro-deposition method in a modulated electrical field in order to have an efficient semiconductor coating on a conductive substrate. The prepared film was used as a photoanode of dye-sensitized solar cells (DSSCs). Electro-deposition of nanoparticles usually was performed by applying a DC electrical field in a suspension. In the DC field, a homogeneous layer could not be performed because of unwanted electrochemical reactions that might occur on the substrate surface. Modulated electrical fields based on pulsed AC and a sweeping voltage profile were used. The photovoltaic performance of the assembled solar cells showed a significant difference between the films produced in different electrical field conditions. Under the illumination of simulated AM 1.5 sunlight (100 mW cm−2) with an aperture black mask, the energy conversion efficiency of 2.45% (V OC = 768 mV, J SC = 4.74 mA cm−2, FF = 67%) was obtained with a thin layer of TiO2 nanoparticles deposited in a pulsed waveform voltage. A crack-free and uniform porous layer produced in this condition showed an enhancement of about seven times over the photoanode prepared using conventional DC electrical field with the same voltage amplitude. The solar cell efficiency was increased to 4.22% (V OC = 735 mV, J SC = 7.92 mA cm−2, FF = 72%) by just increasing the TiO2 film thickness and using a blocking layer beneath the semiconductor layer. Moreover, a higher electron recombination lifetime presented better electron transport and collection efficiency of the film deposited in the pulsed electrical field conditions.