Efficient PbS quantum dot solar cells employing a conventional structure†
New-generation solar cells based on colloidal lead chalcogenide (PbX) quantum dots (CQDs) are promising low-cost solution-processed photovoltaics. However, current state-of-the art CQDs are all using an inverted device architecture. The performance gap between CQD solar cells with conventional and inverted structures is much larger than that for other solution-processed photovoltaics such as organic and perovskite solar cells, which may restrict the future development of CQD solar cells. Here, we reported a record-high power conversion efficiency of 8.45% for conventionally structured PbS QD solar cells by the introduction of a unique conjugated polymer PDTPBT as the anode buffer layer. With the modification of the anode, the device performance was largely improved through a dramatic enhancement in open circuit voltage (Voc), which can be attributed to the enhanced hole extraction to the anode after PDTPBT modification. Meanwhile, the polymer layer can also efficiently improve charge separation and reduce interfacial charge recombination as well as reverse saturation current density, which result in significantly enhanced Voc. More importantly, our results proposed a new conventional architecture for QD solar cells which can avoid the complex processing of metal oxides and is free of light-soaking. This new device structure may offer more flexibility in future device design and show potential advantages in large-scale manufacturing by simplifying the fabrication process.