Evaluation of the recombination processes in DSSC by measuring the open circuit voltage over a wide illumination intensity range

Abstract

The many recombination paths in the dye-sensitized solar cells (DSSCs) differently affect the open circuit voltage (VOC) vs. illumination intensity (G) dependence. In the literature contradictive results concerning the dVOC/dlog(G) gradient ranging from 60 to 120 mV decade−1 exist. To resolve this we have studied the effects of the active layer thickness (d), cell temperature (TC), and, concentration ([]) of ionic liquid (IL) based DSSCs on the dVOC/dlog(G) gradient. The results confirmed that d has only a small effect on the dVOC/dlog(G) gradient, while it is strongly dependent on TC and []. The dVOC/dlog(G) gradient could be as low as 60 mV decade−1 at low [] and low TC, while it may exceed 130 mV decade−1 at higher [] and higher TC. In addition, comparison of theoretical models with experimental results indicates that between 1–100 mW cm−2 the recombination path between the electrons in a tail of shallow traps in TiO2 and the ions prevails.