Design of Experiments (DoE): a multivariate approach to dye-sensitized solar cells comprehension and optimization

Nowadays, modern science proposes and optimizes new materials and technologies, whose characteristics and performances are governed by many factors. However, the scientific community rarely adopts multivariate strategies for the comprehension of what is proposed. As a striking example, a standard dye-sensitized solar cell (DSSC) is a typical complex system assembled with different and heterogeneous layers (FTO/nanocrystalline semiconductor/sensitizer/electrolyte/Pt-FTO), each one affected by intrinsic variability; moreover the layers influence each other and this increases the number of variables involved at the same time in the photoconversion process. The idea of the present work started from the need to identify all the factors by which the photoconversion processes may be influenced. In order to obtain a significant improvement of photovoltaic performances, particularly in reproducibility, long-term stability and efficiency, a chemometric design of experiments (DoE) approach is here presented for four case studies: the formulation of a UV-cured polymer electrolyte membrane, the composition of a cellulose-based gel-polymer electrolyte, the proper sensitization of a ZnO photoanode and the photostability optimization of a series of NIR dyes under different dipping conditions. We are firmly convinced that this approach will make possible to find the optimal experimental conditions to achieve, within a good reproducibility, optimized performances, both in term of efficiency and long term stability.