In the present study, two types of devices were fabricated: DSCs and half-cells, as shown in Fig. 2 and Fig. S1 (ESI †). DSCs are made of two electrodes: the photo electrode (PE) and the counter electrode (CE); the electrolyte in between contains the iodide/triiodide redox pair. PE and CE are each applied to glass coated with a transparent conducting oxide (TCO); the PE includes a mesoporous TiO 2 film sensitized with a dye responsible for light absorption. The CE consists of a nanometric platinum layer applied to the TCO surface that is responsible for catalysing the reduction of triiodide to iodide. A half-cell configuration consisting two identical TCO glasses coated with the relevant material separated the electrolyte. They mimic the phenomena in a DSC allowing the evaluation of CE and electrolyte behaviours without the interference of the sensitized porous TiO 2 layer. In the present study, they were used to study the electrochemical reactions of electrons with electrolyte species over a specific interface. Half-cells made with thin films of SnO 2 -F, Pt, and TiO 2 were assembled to study the recombination reaction as a function of temperature. The preparation of both devices (DSCs and half-cells) is described as follows.
Photoelectrodes were prepared on 2.2 mm thick, 7 O & À1 SnO 2 -F (FTO) coated glass substrates from Solaronix s . First, the glasses were washed sequentially with a detergent solution (Alconox s , VWR) in an ultrasonic cleaner (Amsonic TTC) at 55 1C for 15 min, followed by ultrasonic cleaning in deionized water at room temperature, rinsed with ethanol and dried in air at 50 1C. The samples were then coated with a porous TiO 2 layer by screen-printing a commercial TiO 2 paste (Ti-Nanoxide T/SP from Solaronix s ), followed by drying at 100 1C for 5 minutes. To control the final thickness of the transparent layer of TiO 2 , the screen-printing and drying procedures were repeated as necessary to achieve the desired thickness (12 mm-thick photoelectrodes were obtained with three screen-printing cycles). Samples were annealed at 475 1C for 15 min in an infrared electrical oven (Nabertherm Gmbh model GF75). After firing, the samples were treated with a 40 mM TiCl 4 aqueous solution at 70 1C for 20 minutes before being sintered at 475 1C for 30 min. In the cells, wherein the blocking layer is required, a thin and compact layer of TiO 2 above the FTO layer was applied by immersing the FTO glasses in a 40 mM TiCl 4 aqueous solution at 70 1C for 20 minutes; after washing with water and ethanol, the samples were dried with a nitrogen flow. The counter electrodes, prepared on the same type of glass substrates and cleaned as described before, were drilled previously with two holes, 1 mm in diameter. A commercial platinum based paste (Platisol T/SP from Solaronix s ) was applied on the glass substrate by screen-printing followed by annealing at 400 1C for 15 minutes.
Both in the DSCs and half cells devices, the two electrodes were assembled and sealed using a laser assisted glass frit method. 47 To control the exposed SnO 2 -F area to electrolyte, the glass frit-sealing perimeter was varied from 5 to 12 mm (see Fig. 11) without changing the total distance to the electrical contact; this way the electron lifetime can be controlled without changing the series resistances. Dye adsorption in a porous TiO 2 photoelectrode was obtained by recirculating a dye solution (0.5 mM N719 and 5 M chenodeoxycholic acid in ethanol) for 12 hours using a peristaltic pump (Ismatec s , Reglo Digital MS-4/8), followed by ethanol rinsing, nitrogen drying, electrolyte filling (high stability iodolyte Z-150 from Solaronix s ) and hole sealing by a combination of thermoplastic sealant (Surlyn s , Dupont) and high temperature resistant resin (Pattex s Nural 22 from Henkel). Solder bus bars and electrical wires were applied to the FTO surface of the photo and counter-electrodes, respectively, using an ultrasonic soldering unit (MBR electronics model USS-9210); the soldered bus bars were protected by high temperature resistant resin to prevent corrosion caused by heat and moisture. The manufacture process described produced devices resistant at least to 120 1C without electrolyte leakage. The manufactured DSCs had an energy efficiency between 5% and 6% (25 1C, 100 mW cm À2 , 1.5 air mass filter), which is typical for devices prepared with a non-volatile electrolyte (Iodolyte Z150-Solaronix) based on methoxypropionitrile (MPN), known to produce stable but less efficient devices than that with acetonitrile based electrolytes.
Photoelectrodes were prepared on 2.2 mm thick, 7 O & À1 SnO 2 -F (FTO) coated glass substrates from Solaronix s . First, the glasses were washed sequentially with a detergent solution (Alconox s , VWR) in an ultrasonic cleaner (Amsonic TTC) at 55 1C for 15 min, followed by ultrasonic cleaning in deionized water at room temperature, rinsed with ethanol and dried in air at 50 1C. The samples were then coated with a porous TiO 2 layer by screen-printing a commercial TiO 2 paste (Ti-Nanoxide T/SP from Solaronix s ), followed by drying at 100 1C for 5 minutes. To control the final thickness of the transparent layer of TiO 2 , the screen-printing and drying procedures were repeated as necessary to achieve the desired thickness (12 mm-thick photoelectrodes were obtained with three screen-printing cycles). Samples were annealed at 475 1C for 15 min in an infrared electrical oven (Nabertherm Gmbh model GF75). After firing, the samples were treated with a 40 mM TiCl 4 aqueous solution at 70 1C for 20 minutes before being sintered at 475 1C for 30 min. In the cells, wherein the blocking layer is required, a thin and compact layer of TiO 2 above the FTO layer was applied by immersing the FTO glasses in a 40 mM TiCl 4 aqueous solution at 70 1C for 20 minutes; after washing with water and ethanol, the samples were dried with a nitrogen flow. The counter electrodes, prepared on the same type of glass substrates and cleaned as described before, were drilled previously with two holes, 1 mm in diameter. A commercial platinum based paste (Platisol T/SP from Solaronix s ) was applied on the glass substrate by screen-printing followed by annealing at 400 1C for 15 minutes.
Both in the DSCs and half cells devices, the two electrodes were assembled and sealed using a laser assisted glass frit method. 47 To control the exposed SnO 2 -F area to electrolyte, the glass frit-sealing perimeter was varied from 5 to 12 mm (see Fig. 11) without changing the total distance to the electrical contact; this way the electron lifetime can be controlled without changing the series resistances. Dye adsorption in a porous TiO 2 photoelectrode was obtained by recirculating a dye solution (0.5 mM N719 and 5 M chenodeoxycholic acid in ethanol) for 12 hours using a peristaltic pump (Ismatec s , Reglo Digital MS-4/8), followed by ethanol rinsing, nitrogen drying, electrolyte filling (high stability iodolyte Z-150 from Solaronix s ) and hole sealing by a combination of thermoplastic sealant (Surlyn s , Dupont) and high temperature resistant resin (Pattex s Nural 22 from Henkel). Solder bus bars and electrical wires were applied to the FTO surface of the photo and counter-electrodes, respectively, using an ultrasonic soldering unit (MBR electronics model USS-9210); the soldered bus bars were protected by high temperature resistant resin to prevent corrosion caused by heat and moisture. The manufacture process described produced devices resistant at least to 120 1C without electrolyte leakage. The manufactured DSCs had an energy efficiency between 5% and 6% (25 1C, 100 mW cm À2 , 1.5 air mass filter), which is typical for devices prepared with a non-volatile electrolyte (Iodolyte Z150-Solaronix) based on methoxypropionitrile (MPN), known to produce stable but less efficient devices than that with acetonitrile based electrolytes.