Niobium-doped titanium dioxide nanoparticles for electron transport layers in perovskite solar cells

Nb-doped TiO$_2$ nanoparticles with different doping concentrations, varied from 0 to 2.7 mol. %, were prepared by the sol-gel method followed by thermal treatment. The obtained nanoparticles were used to fabricate a series of electron transport layers for constructing perovskite solar cells (PSCs). The prepared layers were characterized using X-ray diffraction and optical transmission measurements. The effects of Nb doping concentration in TiO$_2$ layers on the optical absorption behavior, the morphology and charge carrier dynamics were studied. A series of PSCs, based on the developed electron transport layers was fabricated and examined. It was found that PSC fabricated with 2.7 mol. % Nb content TiO$_2$ electron transport layer have shown up to 19 % improvement of a power conversion efficiency compared to that, based on an undoped TiO$_2$ layer.