In-situ fabrication of macroporous films for dye-sensitised solar cells: formation of the scattering layer and the gelation of electrolytes

Dye-sensitised solar cells (DSCs) are a promising substitute for conventional silicon solar cells. A scattering layer of submicrometer pores or particles has been widely introduced to achieve a high light-harvesting efficiency. However, many such fabrication processes require high temperatures and multiple steps to prepare the scattering layer. Here, we have developed an in-situ fabrication process for a macroporous (MP) scattering film. The macropores were formed inside the assembled cell via the dissolution of polystyrene (PS) spheres from a PS/TiO2 composite layer caused by exposure to an electrolyte solution. Specifically, the in-situ MP scattering layer decreased the transmittance of the electrode film from 58% to below 1%. The DSCs using these MP scattering layers exhibited an increase in the efficiency of 22%. Moreover, the dissolution of the PS improved the cell stability because of the gelation of the electrolyte solution; the efficiency of the DSCs was maintained at 80% of its initial value after ageing for 20 days, whereas the efficiency of the bare-electrode DSCs was found to have decreased by 50%. We believe that in-situ porous scattering layers show great promise for next-generation flexible DSCs. Moreover, this approach can be extended to various applications that utilize porous film/liquid systems.