CdS/CdSe quantum dots and ZnPc dye co-sensitized solar cells with Au nanoparticles/graphene oxide as efficient modified layer

Co-sensitization by using two or more sensitizers with complementary absorption spectra to expand the spectral response range is an effective approach to enhance device performance of quantum dot sensitized solar cells (QDSSCs). To improve the light-harvesting in the visible/near-infrared (NIR) region, organic dye zinc phthalocyanine (ZnPc) was combined with CdS/CdSe quantum dots (QDs) for co-sensitized solar cells based on ZnO inverse opals (IOs) as photoanode. The resulting co-sensitized device shows an efficient panchromatic spectral response feature to ∼750 nm and presents an overall conversion efficiency of 4.01%, which is superior to that of the individual ZnPc-sensitized solar cells and CdS/CdSe-sensitized solar cells. Meanwhile, an Au nanoparticles/graphene oxide (Au NPs/GO) composite layer was successfully prepared to modify Cu2S counter electrode for the co-sensitized solar cells. Reducing the carrier recombination process by GO and catalytic process of Au NPs leads to increased power conversion efficiency(PCE) from 4.01 to 4.60% and sustainable stability remains ∼85% of its original value after 60 min light exposure. In this paper, introduction of the organic dyes as co-sensitizer and Au NPs/GO as counter electrode modified layer has been proved to be an effective route to improve the performance of QDSSCs.

In this work, we present a new design for the development of QDSSCs based on the macroporous ZnO IOs photoanode sensitized by QDs which have light harvesting in the visible region and organic dye in visible/NIR region. Because of the complementary absorption spectral response caused by CdS/CdSe QDs and ZnPc dye, the co-sensitized solar cell can expand the absorption spectra to ∼750 nm. As a result, the co-sensitized solar cells exhibited a significant improvement in Jsc leading to the overall PCE of 4.01%, which is much better than that of the individual CdS/CdSe (3.08%) or ZnPc (1.88%) sensitizer. We also found that the cell with an Au NPs/GO composite as a modified layer on traditional Cu2S counter electrode shows higher photovoltaic performance (4.60%) which can be attributed to the superior combination of high electro-catalytic activity of Au NPs and the electrical conductivity of the GO network structure. Enhanced stability remains 85% of its original value because ZnPc prevents the degradation of the CdS/CdSe QDs in S2−/Sn2− liquid electrolyte and Au NPs/GO composites catalyse the regeneration of QDs and transmission of carriers. We think the present work can provide a simple stepwise co-sensitization method to improve photoelectric response by expanding the absorption spectrum and an efficient way for green chemistry by modifying the counter electrode with Au NPs/GO composites for QDSSCs.Figure optionsDownload high-quality image (164 K)Download as PowerPoint slide