Photo-driven water splitting photoelectrochemical cells by tandem organic dye sensitized solar cells with I−/I3− as redox mediator

Abstract

Dye-sensitized photoelectrochemical tandem cells have shown the promise for light driven hydrogen production from water owing to the low cost, wide absorption spectra in the visible region and ease to process of their constitutive photoelectrode materials. However, most photo-driven water splitting photoelectrochemical cells driven by organic dye sensitized solar cells exhibit unsatisfactory hydrogen evolution rate, primarily attributed to their poor light capturing ability and low photocurrent performance. Here we present the construction of a tandem system consisting of an organic blue-colored S5 sensitizer-based dye-sensitized photoelectrochemical cell (DSPEC) wired in series with three spectral-complemental dyes BTA-2, APP-3 and APP-1 sensitizers-based dye-sensitized solar cell (DSC), respectively. The two spectral-complemental chromophores were used in DSC and DSPEC to ensure that the full solar spectrum could be absorbed as much as possible. The results showed that the photocurrent of tandem device was closely related to the open-circuit voltage (Voc) of sensitized DSC, in which the tandem configuration consisting of S5 based DSPEC and BTA-2 based DSC gave the best photocurrent. On this basis, tandem device with the only light energy and no external applied electrical bias was further constructed of BTA-2 based 2-junction DSC and S5 based DSPEC and obtained a photocurrent of 500 µA cm−2 for hydrogen generation. Furthermore, I−/I3− was used as a redox couple between dye regeneration and O2 production on the surface of Pt-IrO2/WO3. The strategy opens up the application of pure organic dyes in DSC/DSPEC tandem device.