Figure 2.

P3HT NPs photo-electrochemical characterization. (A) Experimental set-up used for photocurrent action spectrum and chronoamperometry experiments. A planar ITO slab, a saturated KCl Ag/AgCl, and a Pt wire are used as the back contact, the reference (RE) and the counter electrode (CE), respectively. Phosphate Buffer Saline solution at 10 mM molar concentration and pH = 7.0 has been used as the electrolyte. Light is incident from the glass side of the ITO slab. (B) Normalized absorption spectra of P3HT thin solid film (red dashed line) and of NPs dispersion (green solid line) are compared with the P3HT NPs photocurrent action spectrum (red diamonds). The latter was obtained by plotting the steady value of the photocurrent obtained by exciting the NPs dispersion with six narrow-band light sources covering the visible range (emission peak wavelengths at 470, 505, 530, 617, 627, 655 nm). (C) Photocurrent dynamics recorded in P3HT NPs dispersion (light source emission peak wavelength, 470 nm). The red line represents the photocurrent at the OCP value. The blue, green and black lines show the photocurrent signals recorded upon externally applied bias OCP–100 mV, OCP–200 mV, and OCP–300 mV, respectively. The yellow shaded area represents the temporal window corresponding to optical excitation. (D) Photocurrent dynamics with and without molecular oxygen in solution at V = OCP–300 mV. The black solid line represents the photocurrent recorded in ambient conditions (i.e., in equilibrium with the atmosphere). Upon removal of oxygen from the electrolyte and in sealed, nitrogen atmosphere the photocurrent signal is almost completely suppressed (blue solid line). Upon partial re-oxygenation of the electrolyte solution and recovery to the atmospheric equilibrium condition, photocurrent signal is almost completely restored to the initial value (black dashed line). The yellow shaded area represents the temporal window corresponding to optical excitation.