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

• Published in: Physica status solidi. A, Applications and materials science Applications and materials science, 2013-09, Vol.210 (9), p.1750-1757
• Main Authors: Berginc, Marko, Krašovec, Urša Opara, Topič, Marko
• Format: Article
• Language: English
• Subjects: Concentration gradient; dye-sensitized solar cell; Dyes; Illumination; Ionic liquids; light intensity; Open circuit voltage; Photovoltaic cells; recombination process; Solar cells; Studies; Titanium dioxide
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.201329044

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, I3− concentration ([I3−]) 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 [I3−]. The dVOC/dlog(G) gradient could be as low as 60 mV decade−1 at low [I3−] and low TC, while it may exceed 130 mV decade−1 at higher [I3−] 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 I3− ions prevails.