Quantum Dot Photovoltaics in the Extreme Quantum Confinement Regime: The Surface-Chemical Origins of Exceptional Air- and Light-Stability

Type
Article

Authors
Tang, Jiang
Brzozowski, Lukasz
Barkhouse, D. Aaron R.
Wang, Xihua
Debnath, Ratan
Wolowiec, Remigiusz
Palmiano, Elenita
Levina, Larissa
Pattantyus-Abraham, Andras G.
Jamakosmanovic, Damir
Sargent, Edward H.

KAUST Grant Number
KUS-11-009-21

Online Publication Date
2010-01-27

Print Publication Date
2010-02-23

Date
2010-01-27

Abstract
We report colloidal quantum dot (CQDs) photovoltaics having a ∼930 nm bandgap. The devices exhibit AM1.5G power conversion efficiencies in excess of 2%. Remarkably, the devices are stable in air under many tens of hours of solar illumination without the need for encapsulation. We explore herein the origins of this ordersof-magnitude improvement in air stability compared to larger PbS dots. We find that small and large dots form dramatically different oxidation products, with small dots forming lead sulfite primarily and large dots, lead sulfate. The lead sulfite produced on small dots results in shallow electron traps that are compatible with excellent device performance; whereas the sulfates formed on large dots lead to deep traps, midgap recombination, and consequent catastrophic loss of performance. We propose and offer evidence in support of an explanation based on the high rate of oxidation of sulfur-rich surfaces preponderant in highly faceted large-diameter PbS colloidal quantum dots. © 2010 American Chemical Society.

Citation
Tang J, Brzozowski L, Barkhouse DAR, Wang X, Debnath R, et al. (2010) Quantum Dot Photovoltaics in the Extreme Quantum Confinement Regime: The Surface-Chemical Origins of Exceptional Air- and Light-Stability. ACS Nano 4: 869–878. Available: http://dx.doi.org/10.1021/nn901564q.

Acknowledgements
We thank Vlad Sukhovatkin, Kyle Kemp, Ghada Koleilat, Illan Kramer, and Steven Huang for their assistance and insights. J. Tang thanks Dr. Dan Grozea, Dr. Srebri Petrov and Dr. Haizheng Zhong for material characterization and fruitful discussion. R. Debnath acknowledges the financial support of an e8 scholarship. This publication was supported in part by Award No. KUS-11-009-21 made by King Abdullah University of Science and Technology (KAUST).

Publisher
American Chemical Society (ACS)

Journal
ACS Nano

DOI
10.1021/nn901564q

PubMed ID
20104859

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