Fig. 3: Optoelectronic characterisation of the photovoltaic pixel.

a Picture of the KPFM setup. b Surface voltage changes obtained with Ti (circles) and TiN-coated (squares) cathodes. Each bar is the mean (± s.d.) of the measures from n = 13 Ti pixels and n = 8 TiN-coated pixels. c Drawing of the experimental setup for the measure of the PC and PV; the light pulse comes from the bottom. d, e Mean PCD (d) and PV (e) measures obtained from Ti (grey) and TiN-coated (black) pixels upon illumination (565 nm, 10 ms, 0.9 mW mm⁻²). For Ti, n = 24 pixels from four chips were averaged; for TiN, n = 18 pixels from three chips were averaged. f, g Mean (± s.e.m) PCD (f) and PV (g) amplitudes quantified at increasing irradiance levels (565 nm, 10 ms) for Ti pixels (circles; n = 24 pixels from four chips) and TiN-coated pixels (squares; n = 18 pixels from three chips). h Mean (± s.e.m) PCD and PV amplitudes quantified at 0.9 mW mm⁻² for Ti (n = 24 pixels from four chips) and TiN-coated (n = 18 pixels from three chips) pixels. i AFM images of the Ti and Ti/TiN surfaces. The colour bar shows the surface roughness. j Mean (± s.d.) percental increase of the surface area compared to the nominal flat area (500 × 500 nm²).