Fabrication and electrical characteristics of halide-terminated nanocrystal thin films
Jonathan Owen a, Nicholas Anderson a, Zachariah Norman a
a Columbia University, US, Broadway, 3000, New York, United States
Invited Speaker, Jonathan Owen, presentation 003
Publication date: 1st April 2013


Numerous attempts to utilize semiconductor nanocrystals in photovoltaic devices have consistently demonstrated low power conversion efficiencies, usually in the range of 1-5%.1,2 Organic surfactants bound to nanocrystals are at the heart of this problem because they prevent efficient charge transport and at the same time passivate surfaces against charge trapping.To overcome this problem, we are developing techniques to exchange organic surfactants with halide ligands that maintain surface passivation and allow efficient charge transport. My talk will describe our investigations of halide-terminated nanocrystals in solution and in thin-films.  In particular, we have exchanged carboxylate ligands for chloride ligands in the presence of alkylphosphines and prepared thin film transistors with unusually high electron mobilities (8 cm^2/V/sec). In addition, I will discuss the important role that ligands play in passivating surface traps and strategies to balance defect passivation with efficient exciton dissociation.

(1) Kamat, P. V. Quantum Dot Solar Cells. Semiconductor Nanocrystals as Light Harvesters. J. Phys. Chem. B 2008, 112, 18737-18753. (2) Kramer, I. J.; Sargent, E. H. Colloidal Quantum Dot Photovoltaics: A Path Forward. ACS Nano 2011, 5, 8506–8514. (3) Talapin, D. V.; Lee, J.-S.; Kovalenko, M. V.; Shevchenko, E. V. Prospects of Colloidal Nanocrystals for Electronic and Optoelectronic Applications. Chem. Rev. 2010, 110, 389-458.
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