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Fast, sensitive and spectrally tuneable colloidal-quantum-dot photodetectors


Solution-processed semiconductors are compatible with a range of substrates, which enables their direct integration with organic circuits1,2, microfluidics3,4, optical circuitry1,5 and commercial microelectronics. Ultrasensitive photodetectors based on solution-process colloidal quantum dots operating in both the visible and infrared have been demonstrated6,7, but these devices have poor response times (on the scale of seconds) to changes in illumination, and rapid-response devices based on a photodiode architecture suffer from low sensitivity8. Here, we show that the temporal response of these devices is determined by two components—electron drift, which is a fast process, and electron diffusion, which is a slow process. By building devices that exclude the diffusion component, we are able to demonstrate a >1,000-fold improvement in the sensitivity–bandwidth product of tuneable colloidal-quantum-dot photodiodes operating in the visible and infrared6,7,8.

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Figure 1: Photodiode structure, energy bands and photocurrent components.
Figure 2: Photodiode spectral response, illumination response and frequency response.
Figure 3: Photodiode transient response and quantum efficiency as a function of bias and irradiance.
Figure 4: Fully depleted photodiode spectral response and frequency response.


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The authors thank D. Grozea for performing the XPS measurements.

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Authors and Affiliations



J.P.C conceived and fabricated the CQD photodiodes, performed all device performance characterization, and conceived and implemented the CQD photodiode device model. G.K. coordinated and interpreted the XPS measurements. K.W.J. and J.P.C co-developed the first step of the CQD surface modification strategy. S.H. and J.P.C. co-developed the second step of the CQD surface modification strategy. L.L. synthesized all CQDs used to fabricate the devices. E.H.S. assisted in interpretation of the results, commented on the device model, and commented on the manuscript. All authors discussed the results and the capacity of the model to describe the underlying physics of device operation.

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Correspondence to Edward H. Sargent.

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Clifford, J., Konstantatos, G., Johnston, K. et al. Fast, sensitive and spectrally tuneable colloidal-quantum-dot photodetectors. Nature Nanotech 4, 40–44 (2009).

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