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

The many recombination paths in the dye-sensitized solar cells (DSSCs) differently affect the open circuit voltage (V-OC) vs. illumination intensity (G) dependence. In the literature contradictive results concerning the dV(OC)/dlog(G) gradient ranging from 60 to 120mVdecade(-1) exist. To resolve this we have studied the effects of the active layer thickness (d), cell temperature (T-C), and, I3- concentration ([I3-]) of ionic liquid (IL) based DSSCs on the dV(OC)/dlog(G) gradient. The results confirmed that d has only a small effect on the dV(OC)/dlog(G) gradient, while it is strongly dependent on T-C and [I3-]. The dV(OC)/dlog(G) gradient could be as low as 60mVdecade(-1) at low [I3-] and low T-C, while it may exceed 130mVdecade(-1) at higher [I3-] and higher T-C. In addition, comparison of theoretical models with experimental results indicates that between 1-100mWcm(-2) the recombination path between the electrons in a tail of shallow traps in TiO2 and the I3- ions prevails. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim