A layer-by-layer ZnO nanoparticle-PbS quantum dot- self-assembly platform for ultrafast interfacial electron injection

A layer-by-layer ZnO nanoparticle-PbS quantum dot- self-assembly platform for ultrafast interfacial electron injection

A layer-by-layer ZnO nanoparticle-PbS quantum dot- self-assembly platform for ultrafast interfacial electron injection
Mohamed Eita, Anwar Usman, Ala’a O. El-Ballouli, Erkki Alarousu, Osman M. Bakr, and Omar F. Mohammed
Small, 11(1), pp 112-118, (2015)
Mohamed Eita, Anwar Usman, Ala’a O. El-Ballouli, Erkki Alarousu, Osman M. Bakr, and Omar F. Mohammed
Layer-by-layer ZnO nanoparticles, PbS quantum dots, Heterojunction, Electron injection, Femtosecond transient absorption spectroscopy
2015

Absorbent layers of semiconductor quantum dots (QDs) are now used as material platforms for low-cost, high-performance solar cells. On the other hand, the semiconductor metal oxide nanoparticles as an acceptor layer became an integral part of the next generation solar-cell devices. To achieve sufficient electron transfer and subsequently high conversion efficiency in these solar cells, however, energy-level alignment and interfacial contact between the donor and the acceptor units are needed. Here, we introduce the layer-by-layer (LbL) technique to assemble ZnO nanoparticles (NPs) that provides adequate PbS QD uptake to achieve greater interfacial contact compared with traditional sputtering methods. We also investigate electron injection at the PbS QD and ZnO NP interfaces using broadband transient absorption spectroscopy with 120 femtosecond time resolution. The transient absorption data indicate that electron injection from photoexcited PbS QDs to ZnO NPs occurs on a time scale of a few hundred femtoseconds. This observation is supported by the interfacial electronic-energy alignment between the donor and acceptor moieties. Finally, due to the combination of large interfacial contact and ultrafast electron injection, our proposed platform of assembled thin films holds promise for a variety of solar cell architectures and other settings that principally rely on interfacial contact, such as photocatalysis.



DOI: 10.1002/smll.201400939