Highly Efficient Inverted Structural Quantum Dot Solar Cells

Abstract

Highly efficient PbS colloidal quantum dot (QD) solar cells based on an inverted structure have been missing for a long time. The bottlenecks are the construction of an effective p–n heterojunction at the illumination side with smooth band alignment and the absence of serious interface carrier recombination. Here, solution-processed nickel oxide (NiO) as the p-type layer and lead sulfide (PbS) QDs with iodide ligand as the n-type layer are explored to build a p–n heterojunction at the illumination side. The large depletion region in the QD layer at the illumination side leads to high photocurrent. Interface carrier recombination at the interface is effectively prohibited by inserting a layer of slightly doped p-type QDs with 1,2-ethanedithiol as ligands, leading to improved voltage of the device. Based on this graded device structure design, the efficiency of inverted structural heterojunction PbS QD solar cells is improved to 9.7%, one time higher than the highest efficiency achieved before.

An inverted structural QD solar cell with a p–n heterojunction located at the illumination side is constructed and, exhibits remarkably high photocurrent above 27 mA cm⁻². The insertion of an intermediate buffer layer effectively reduces interface recombination, giving rise to improved voltage. The power conversion efficiency is improved to 9.7%, which is doubled for inverted structural heterojunction QD solar cells.

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