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 d V OC /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 ( T C ), and,I 3 −concentration ([ I 3 − ]) of ionic liquid (IL) based DSSCs on the d V OC /dlog( G ) gradient. The results confirmed that d has only a small effect on the d V OC /dlog( G ) gradient, while it is strongly dependent on T C and [ I 3 − ]. The d V OC /dlog( G ) gradient could be as low as 60 mV decade −1 at low [ I 3 − ] and low T C , while it may exceed 130 mV decade −1 at higher [ I 3 − ] and higher T C . 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 TiO 2 and theI 3 −ions prevails.