Ricerc@Sapienza

The cost-effective production of chemicals in electrolytic cells and the conversion of the radiation energy into electrical energy in photoelectrochemical cells (PECs) require the use of electrodes with large surface area, which possess either electrocatalytic or photoelectrocatalytic properties. In this context nanostructured semiconductors are electrodic materials of great relevance because of the possibility of varying their photoelectrocatalytic properties in a controlled fashion via doping, dye-sensitization or modification of the conditions of deposition.

In the framework of the research on dye-sensitized solar cells of p-type (p-DSCs) the definition and optimization of the electrolyte have been a crucial aspect for the reach of the recent records of photo-conversion for these devices. At the basis of this progress there was the replacement of the redox shuttle of reference I-3(-)/I- with opportune redox mediators which deliver higher photocurrents and produce larger open circuit photovoltages.

In p-type dye sensitized solar cells (p-DSCs) with nickel oxide (NiO) based photocathodes one of the main causes of their relatively poor photoconversion performances is the fast recombination between the photoinjected holes in the valence band of the p-type semiconductor and the reduced form of the redox shuttle (typically I−). As a matter of fact, recombination phenomena at the NiO/electrolyte interface heavily limit both photovoltage and photocurrent.

In this work we present the electrochemical and photoelectrochemical characterization of NiO thin films [thickness (l) range: 2 <= l <= 4 mu m], which have been obtained from screen-printing of three precursor-pastes. All three pastes contained preformed NiO nanoparticles [diameter ((MT SET)) range: 20 < ((MT SET)) < 50 nm], but differed for the content and nature of the acidic component. The resulting NiO samples were employed as photoactive cathodes of p-type dye-sensitized solar cells (p-DSCs).