Ultraviolet light can improve smartphone cameras

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Photodetectors ultraviolet light
Desorption of oxygen under the influence of UV radiation.

Photodetectors are used in a wide range of systems and devices, from smartphones to space stations.

They are typically only sensitive to light within a certain narrow bandwidth, which causes numerous problems to product developers.

Now researchers from China and Saudi Arabia have found a way to address this issue. According to their study, treating a common photodetector with ultraviolet light can turn it into a high bandwidth device.

The finding is published in Advanced Functional Materials.

Currently, there is a lot of demand for photodetectors that are sensitive to a wide range of frequencies, but they are difficult to design.

It’s hard to find the right materials, because the substances that permit ultraviolet light tend to be nontransparent to infrared radiation, and vice versa.

In this study, researchers found a way to ‘broaden’ the spectral response of photodetectors.

The research team studied polymer photodetectors based on the internal photoelectric effect, i.e., the redistribution of electrons within a polymer under the influence of light, resulting in electrical conductivity.

Photodetectors based on organic materials have a number of advantages over their conventional inorganic counterparts, including their low cost, easier manufacturing, and physical flexibility.

It turned out that by interacting with the surfaces of certain elements of the device, UV radiation could alter its sensitivity.

The researchers conducted an experiment, in which a polymer-based photodetector incorporating zinc oxide (ZnO) nanoparticles was exposed to UV light for 30 seconds.

As a result of this, they achieved a high-performance photodetector with a much broader spectral response and a maximum external quantum efficiency of 140,000%, as compared to the 30% measured before UV treatment.

However, the noise experienced by the device was also greater due to an increased dark current, which is generated in the detector even when no photons are entering the device.

The researchers attribute the dramatic effect of UV light on detectors to the detachment of oxygen atoms from the zinc oxide molecules.

Researchers suggest that people can thus convert a polymer-based photodetector into a highly sensitive broadband device.

The process itself is quick, cheap, and efficient, which is important for practical applications.

In the future, the researchers will eliminate the “side effects” that arise after irradiating the detector with UV light (e.g., a sharp increase in dark current), without sacrificing the high performance and wide spectral range of the device.

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Citation: Zhou X, et al. (2016). Ultrahigh Gain Polymer Photodetectors with Spectral Response from UV to Near-Infrared Using ZnO Nanoparticles as Anode Interfacial Layer. Advanced Functional Materials, published online. DOI: 10.1002/adfm.201601980.
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