The dye-sensitized solar cells (DSCs) based on an organic sensitizer with trade name RK1 were fabricated by new fabrication procedure. The fabrication procedure that performed in inert gas atmosphere using a glove box includes: (i) assembling sandwich cells from preparative FTO/TiO₂ and FTO/Pt electrodes; (ii) filling the cells with RK1 (10 mM)/DMF solutions containing 0–10 mM chenodeoxycholic acid (CDA) and keep still for 4 hours; (iii) filling the electrolyte; and (iv) sealing the cells. In high humidity environment this new proposed procedure has proved to prevent the water uptake into the cell.

In comparison with co-adsorbate free DSCs, the energy conversion efficiency (η) of DSCs with presence of co-adsorbate was improved. However, the photo-activation effect (slight increase of η) observed during first weeks of outdoor test for DSCs with CDA co-adsorbate is lesser than that of co-adsorbate free DSCs. From 14^th day of outdoor test the cell efficiency began slightly decrease, and reached the initial value after 21-day-exposure. Meanwhile for the co-adsorbate free DSCs these dates are 30^th and 100^th, respectively.

The electrochemical impedance spectroscopy (EIS) technique was successfully applied to study electronic and ionic processes in DSC, and consequently, to evaluate the effect of co-adsorbate on cells performance and outdoor stability. The impedance data measured at open circuit voltage (V_oc) under illumination were well fitted with the equivalent circuit R_s(R_PtC_dl)G(C_dR_d), in which R_s – electrolyte solution resistance, R_Pt and C_dl describe the modeled charge transfer resistance and capacitance at the counter electrode. The electron transport in the titanium dioxide (TiO₂) film and the back reaction at the TiO₂/electrolyte interface were modeled by a Gerischer element (G), revealed by an arc at the intermediate-frequency region. The R_dC_d circuit elements describe the  ion diffusion in the electrolyte.

Analysis of impedance spectra indicated that the increase of electron injection via the effect of co-adsorption contributed to enhancement of photocurrent. This fact was revealed by the decrease of Gerischer impedance. Meanwhile the increase of photocurrent which caused the photo-activation of the cathode interface during first weeks of outdoor exposure was interpreted by the decrease of charge transfer resistance R_Pt. EIS data show that DSC performance declines under prolonged outdoor exposure. The DSC ageing resulted mainly from the decrease of electron injection in TiO₂ film.