Introduction of polysulfide anions to increase the loading quantity of PbS quantum-dots for efficient solid-state quantum-dot sensitized TiO2 nanorod array solar cells

To increase the loading quantity of PbS quantum-dots, the polysulfide anion (S22−) was firstly introduced in successive ionic layer absorption and reaction process to prepare PbS quantum-dot thin films on TiO2 nanorod arrays. The influence of polysulfide anion (S22−) concentrations in the precursor solution on the deposition of PbS quantum-dot thin films was systematically investigated and the photovoltaic performance of the corresponding solid-state PbS quantum-dot sensitized solar cells with spiro-OMeTAD was evaluated. The loading quantity and crystallinity of PbS quantum-dots increased with the increase of polysulfide anion (S22−) concentrations from 0 to 1 mM and 2 mM. When the polysulfide anion (S22−) concentration was 1 mM and the surface of TiO2 nanorod arrays was modified by 3-mercaptopropionic acid, the optimal photoelectric conversion efficiency of 4.75% was achieved, along with the open-circuit voltage of 0.56 V, short-circuit photocurrent density of 13.00 mA cm−2 and fill factor of 64.8%. The photoelectric conversion efficiency of 4.75% was relatively high in solid-state PbS quantum-dot sensitized solar cells using successive ionic layer absorption and reactions.