Observation of the dye-sensitised solar cell (DSSC) physical mechanism cannot be carried out experimentally; therefore, an analysis using a model is needed to explain the mechanism. In this article, DSSC is modelled as a series comprising a diode and other electronic components, including a photocurrent (Iph), saturation current (I0), series resistance (Rs), parallel resistance (Rp) and the ideality factor of the diode (n). These electronic components are called DSSC internal parameters. This study aims to find the value of DSSC internal parameters with variations of working electrode thickness. The particle swarm optimisation (PSO) algorithm as an optimisation method is used to achieve the aim. The model indicates that by increasing the thickness, the photocurrent rises and the parallel resistance decreases.