Solid-state and flexible dye-sensitized TiO2 solar cells:: a study by electrochemical impedance spectroscopy

Dye-sensitized TiO2 solar cells were assembled using rigid or flexible transparent electrodes (a conductive film deposited on glass or on poly(ethylene terephthalate) as substrates and a polymer electrolyte based on I-3(-)/I- and poly(epichlorohydrin-co-ethylene oxide)). The cells were characterized by current-potential curves and electrochemical impedance spectroscopy under different light intensities. Under 100 mW cm(-2) illumination, the rigid cell exhibited an open circuit potential V-OC = 0.82 V, a short-circuit photocurrent I-SC 2.2 mA cm(-2), and an efficiency eta = 1%; for the flexible cell, V-OC = 0.72 V, I-SC = 0.40 mA cm(-2), and eta = 0.1%. Under illumination, impedance spectra of the cells exhibited three semicircles. In the dark, both systems presented very high impedance. The differences in the efficiency and the impedance spectra of both cells were compared and discussed.