All solid state multiply layered PbS colloidal quantum-dot-sensitized photovoltaic cells

The combination of solution processable colloidal quantum dots (CQDs) and organic conjugated polymers has attracted growing interest in the past few years, because devices fabricated using this combination can have potentially low cost and high efficiency. In this paper, we propose a new device architecture of multiply layered PbS CQD-sensitized photovoltaic cells. The multiple layers of PbS CQDs were formed by the repeated spin-coating of oleic-acid-capped PbS CQD solution and 1 wt% 1,2-ethanedithiol (EDT) solution onto mesoporous (mp)-TiO2 as photoanode. Through the structural advantage of a sensitized type device and post-treatment in 10 wt% EDT solution for 16 h, we could fabricate efficient photovoltaic cells having an overall energy conversion efficiency of 2.9% under 1 sun illumination, and an external quantum efficiency of over 15% at zero bias with a signal attenuation to frequency of 10 kHz levels in the near-infrared (NIR) range.