Methods of measuring energy conversion efficiency in dye-sensitized solar cells

The current-voltage characteristics of dye-sensitized solar cells (DSCs) were measured and compared with those of crystalline silicon solar cells. It was found that the energy conversion efficiency of DSCs is dependent on voltage sweep direction and sampling delay time (T-d). Measurement of the transient photocurrent revealed that this dependence is due to the longer time constant of DSCs. This dependence was also confirmed in a simulation of current-voltage curves based on an equivalent circuit model of DSCs. Analysis of the current-voltage characteristics of polymer-based bulk heterojunction solar cells (BHSCs) and simulated measurements showed that the longer time constant is due to slow movement of ions in the electrolyte. To improve accuracy, the I-V measurement should be carried out from short circuit to open circuit with T-d of 100 ms or longer.