Synergistic enhancement of charge generation and transfer in organic solar cells via a separate PbS quantum dot layer

The major impediment to the high photovoltaic performance of organic solar cells (OSCs) involves deficient photon harvesting and ineffective charge transfer from the photoactive layer to the electrodes. To improve these constraints, in this study, a new OSC device architecture is demonstrated by incorporating PbS colloidal quantum dots (QDs) between the organic photoactive layer and the top electrode. PbS QDs were spin-coated on top of an organic blend via a layer-by-layer deposition process, which formed a separate PbS QD layer with high density and uniformity. The PbS QD layer reinforced the optical property of the OSC by harvesting photons that were not absorbed by the underlying organic photoactive layer. In addition, the OSC employing the QD layer showed the enhanced charge transfer and suppressed recombination loss through the hybrid organic-inorganic interfacial contacts. Thus, a significant increase in the efficiency was achieved compared with the OSC with no PbS QD layer (10.12 vs 8.84%). Accompanied with the improved optoelectronic properties, a superior stability of the proposed architecture advances the practical viability of OSCs in various applications. • Organic solar cells (OSCs) employing a quantum dot (QD) layer are demonstrated. • The PbS QD layer provides complementary photo-generation of charge carriers. • The charge transfer is improved at the organic blend-PbS QD hybrid interfaces. • An enhancement in the efficiency while pursuing superior stability is achieved. • The QD layer platform promises new opportunities in organic optoelectronic devices.