Towards the low cost manufacture of dye-sensitized solar cells using inkjet technology

This work presents a novel means of producing dye-sensitized solar cells (DSSCs), using an inkjet printing technique. To manufacture a completely inkjet-printed DSSC, all layers must be considered and a thorough analysis of the suitability of the printing process has previously been unreported. For DSSCs to become commercially viable they must have long term operational stability, be efficient, have a low environmental impact and low manufacturing cost. Inkjet printing is an additive manufacturing process, meaning that material is only deposited where needed, minimising the material wastage. Several nanoparticle materials were investigated including titanium dioxide (TiO2), carbon black as a low cost replacement for platinum and PEDOT:PSS as a low cost replacement to the widely used spiro-MeOTAD 92,2' ,7,7'-tetrkis(N,N-di-p-methoxyphenylamine)-9,9-spirobifluorene) solid-state hole transport material. A highly porous network of metal-oxide nanocrystals is a fundamental building block to produce DSSCs. The morphology of this layer can greatly influence the efficiency of the cell and therefore a significant amount of this project was spent on developing suitable ink and printing this layer. Titanium dioxide (TiO2) is widely used within the development of photoanodes due to its low cost, stability and low impact on the environment. However, it can be difficult to create a stable dispersion within water due to the natural tendency for the material to agglomerate. An aqueous TiO2 nanoparticle dispersion was developed and several additive materials were explored in an effort to optimize the ink. The initial ink was printed to produce a layer 2.6 μm thick which, once incorporated into a DSSC, resulted in a promising efficiency of 3.50%. Inkjet printed carbon black counter electrodes with thicknesses of 10.24 μm, lead to efficiencies of 2.59%, whilst inkjet printed PEDOT:PSS solid state hole transport material resulted in a very low efficiency of 0.08%. Whilst the PEDOT:PSS and carbon did not produce suitable results for this application, it is suggested that further materials are still investigated due to the benefits of the manufacturing technique. Therefore, it can be concluded that this work shows the capability of inkjet printing for low-cost solar cells, with exciting potential application to other printed electronic applications