Publications

Overcoming the cut-off charge transfer bandgaps at the Pbs quantum dot interface

Overcoming the cut-off charge transfer bandgaps at the Pbs quantum dot interface
Ala’a O. El-Ballouli, Erkki Alarousu, Ahmad R. Kirmani, Aram Amassian, Osman M. Bakr, and Omar F. Mohammed
Advanced Functional Materials, 25(48), pp 7435-7441, (2015)
Ala’a O. El-Ballouli, Erkki Alarousu, Ahmad R. Kirmani, Aram Amassian, Osman M. Bakr, and Omar F. Mohammed
Quantum dots, Photovoltaic devices, Charge carrier injection, Time-resolved spectroscopy, Interfacial electrostatic interaction
2015
Light harvesting from large size of semiconductor PbS quantum dots (QDs) with a band gap of less than 1 eV is one of the greatest challenges precluding the development of PbS QD-based solar cells because the interfacial charge transfer (CT) from such QDs to the most commonly used electron acceptor materials is very inefficient, if it occurs at all. Thus, an alternative electron-accepting unit with a new driving force for CT is urgently needed to harvest the light from large-sized PbS QDs. Here, we utilize a cationic porphyrin as a new electron acceptor unit with unique features that bring the donor-acceptor components into close molecular proximity, allowing ultrafast and efficient electron transfer for QDs of all sizes, as inferred from the drastic photoluminescence (PL) quenching and the ultrafast formation of the porphyrin anionic species. Our time-resolved results clearly demonstrate the possibility of modulating the electron transfer process between PbS QDs and porphyrin moieties not only by the size quantization effect but also by the interfacial electrostatic interaction between the positively charged porphyrin and the negatively charged QDs. This approach provides a new pathway for engineering QD-based solar cells that make the best use of the diverse photons making up the Sun’s broad irradiance spectrum.


DOI: 10.1002/adfm.201504035