Air-processed depleted bulk heterojunction solar cells based on PbS/CdS core–shell quantum dots and TiO2 nanorod arrays

Abstract

All solution processed depleted bulk heterojunction (DBH) solar cell devices based on near infrared (NIR) PbS/CdS core–shell quantum dots (QDs) and films of rutile TiO2 nanorod arrays have been investigated. The device fabrication was achieved through the layer-by-layer spin coating of PbS/CdS QDs, in ambient atmosphere, onto hydrothermally grown TiO2 nanorod arrays film leading to the general device architecture consisting of fluorine doped tin oxide (FTO)/TiO2/QDs/interfacial layer/Au. The performance of these devices fabricated under different processing conditions was tested and compared with that of similar devices where the PbS/CdS QDs were replaced by a spin-coated layer of colloidal PbS QDs (processed under inert atmosphere). It was found that the maximum power conversion efficiency of the former devices is about 40% higher when MoO3 was used as an interfacial layer (2.02%±0.15 vs 1.40%±0.11). The stability and ease of processing in air together with the higher performance of the PbS/CdS core–shell QDs, as compared to the PbS QDs, strongly suggest their high potential in solar cell applications. This work represents the first demonstration of the use of NIR PbS/CdS core–shell QDs in solar cells.