Spectral sensitization of TiO₂ with electrodeposited PbSe: improvement of photocurrent stability and light conversion efficiency

Highlights: •TiO₂ was sensitized for visible light with electrodeposited PbSe. •Stable anodic photocurrent is achieved in the presence of SeSO₃²⁻ ions. •TiO₂/PbSe photoanodes were used in photoelectrochemical cells. •Photocurrent conversion efficiency was fourfold improved by Nb doping in TiO₂. -- Abstract: This work focuses on spectral sensitization of mesoporous TiO₂ films and Nb-doped TiO₂ films with polydisperse PbSe nanoparticles (TiO₂/PbSe). For this, PbSe was electrochemically deposited from aqueous solution containing Pb²⁺ cations and SeO₂. Chemical amount of electrodeposited PbSe was controlled by deposition time and impacted on the magnitude of sensitized photocurrents. The efficacy of different ions (S_n²⁻; I₃⁻; H₂PO₄⁻; N₂H₅⁺; SO₃²⁻; SCN⁻, SeSO₃²⁻) as hole scavengers for TiO₂/PbSe photoanodes was assessed by dynamics of photocurrent in polarization measurements. Electrolyte of Na₂SO₃ and Na₂SeSO₃ is reported as an effective one to attain stable photocurrent. Photoelectrochemical cells with TiO₂/PbSe photoanodes show solar to electricity conversion efficiency of 0.09%, in spectral region up to 700 nm for undoped TiO₂. Enhancement of the photoresponse was achieved by different level of Nb doping into mesoporous TiO₂ film. Extension of spectral response up to 800 nm and photocurrent conversion efficiency of 0.24% is observed for TiO₂/PbSe photoanodes with 2.5 at% Nb-doped TiO₂. Doping with Nb results in positive shift on electrochemical scale of conduction band of TiO₂. It favors the collection of photoelectrons from PbSe nanoparticles that have light absorption in wider spectral region.