Colloidal-quantum-dot (CQD) optoelectronics offer a compelling combination of solution processing and spectral tunability through quantum size effects. So far, CQD solar cells have relied on the use of organic ligands to passivate the surface of the semiconductor nanoparticles. Although inorganic metal chalcogenide ligands have led to record electronic transport parameters in CQD films, no photovoltaic device has been reported based on such compounds. Here we establish an atomic ligand strategy that makes use of monovalent halide anions to enhance electronic transport and successfully passivate surface defects in PbS CQD films. Both time-resolved infrared spectroscopy and transient device characterization indicate that the scheme leads to a shallower trap state distribution than the best organic ligands. Solar cells fabricated following this strategy show up to 6% solar AM1.5G power-conversion efficiency. The CQD films are deposited at room temperature and under ambient atmosphere, rendering the process amenable to low-cost, roll-by-roll fabrication.
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This publication is based in part on work supported by Award No. KUS–11–009-21, made by King Abdullah University of Science and Technology (KAUST). We thank Angstrom Engineering and Innovative Technologies for useful discussions concerning material deposition methods and control of the glovebox environment, respectively. The authors thank H. Zhong, R. Li, L. Brzozowski, V. Sukhovatkin, A. Barkhouse, I. Kramer, G. Koleilat, E. Palmiano and R. Wolowiec for their help during the course of study. R.D. acknowledges the financial support of e8 scholarship. K.S.J. and J.B.A. gratefully acknowledge partial support from the Petroleum Research Fund (PRF #49639-ND6), the National Science Foundation (CHE 0846241), and the Office of Naval Research (N00014-11-1-0239).
The authors declare no competing financial interests.
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Tang, J., Kemp, K., Hoogland, S. et al. Colloidal-quantum-dot photovoltaics using atomic-ligand passivation. Nature Mater 10, 765–771 (2011). https://doi.org/10.1038/nmat3118
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