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Solution-processed PbS quantum dot infrared photodetectors and photovoltaics


In contrast to traditional semiconductors, conjugated polymers provide ease of processing, low cost, physical flexibility and large area coverage1. These active optoelectronic materials produce and harvest light efficiently in the visible spectrum. The same functions are required in the infrared for telecommunications (1,300–1,600 nm), thermal imaging (1,500 nm and beyond), biological imaging (transparent tissue windows at 800 nm and 1,100 nm), thermal photovoltaics (>1,900 nm), and solar cells (800–2,000 nm). Photoconductive polymer devices have yet to demonstrate sensitivity beyond 800 nm (refs 2,3). Sensitizing conjugated polymers with infrared-active nanocrystal quantum dots provides a spectrally tunable means of accessing the infrared while maintaining the advantageous properties of polymers. Here we use such a nanocomposite approach in which PbS nanocrystals tuned by the quantum size effect sensitize the conjugated polymer poly[2-methoxy-5-(2′-ethylhexyloxy-p-phenylenevinylene)] (MEH-PPV) into the infrared. We achieve, in a solution-processed device and with sensitivity far beyond 800 nm, harvesting of infrared-photogenerated carriers and the demonstration of an infrared photovoltaic effect. We also make use of the wavelength tunability afforded by the nanocrystals to show photocurrent spectra tailored to three different regions of the infrared spectrum.

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Figure 1: Dark current and photocurrent versus applied bias at the ITO electrode.
Figure 3: Photocurrent spectral responses and absorption spectra.
Figure 2: Photocurrent and internal quantum efficiency versus incident optical power.

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We thank S. Hoogland for discussions and the following for support: the Government of Ontario through the Ontario Graduate Scholarships program (S.A.M.); Materials and Manufacturing Ontario, a division of the Ontario Centres of Excellence; the Natural Sciences and Engineering Research Council of Canada through its Collaborative Research and Development Program; Nortel Networks; the Canada Foundation for Innovation; the Ontario Innovation Trust; and the Canada Research Chairs Programme.

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Correspondence to Edward H. Sargent.

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McDonald, S., Konstantatos, G., Zhang, S. et al. Solution-processed PbS quantum dot infrared photodetectors and photovoltaics. Nature Mater 4, 138–142 (2005).

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