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Scientists unveil record-setting flexible phototransistor

Researcher Zhenqiang "Jack" Ma says the phototransistor's combination of high performance and flexibility "have never been achieved at the same time."
By Brooks Hays   |   Oct. 30, 2015 at 3:41 PM

MADISON, Wis., Oct. 30 (UPI) -- World, meet the fastest, most responsive flexible silicon phototransistor ever made -- brought to you by the scientists of the University of Wisconsin.

The technology outperforms all previous flexible phototransistors in terms of sensitivity and response time, and can be integrated into a variety of devices, from digital cameras and night-vision goggles, satellites to medical imaging instruments.

Employed in a camera, the phototransistor could eventually deliver clearer, higher definition images, especially in low-light conditions.

Phototransistors act like the eyes of mammals, collecting light and turning it into an electrical pulse. In mammals, that pulse is carried by nerves to the brain. In digital devices, the electromagnetic data is transcribed as a binary code, which is turned into an image by software.

One of the innovations that makes the new phototransistor so effective is a technique called "flip-transfer" fabrication. The almost-finished phototransistor is inverted onto a thin plastic film with a metal layer on the bottom.

Beneath the ultrathin silicon nanomembrane layer are electrodes, which along with the metal layer, improve light absorption.

"In this structure -- unlike other photodetectors -- light absorption in an ultrathin silicon layer can be much more efficient because light is not blocked by any metal layers or other materials," Zhenqiang "Jack" Ma, professor of electrical and computer engineering at Wisconsin, said in a press release.

The tag-teaming bottom layer metal and electrodes negate the need for an external amplifier.

"There's a built-in capability to sense weak light," Ma explained.

And because it's flexible, the technology can be applied in a variety of capacities.

"This demonstration shows great potential in high-performance and flexible photodetection systems," concluded Ma. "It shows the capabilities of high-sensitivity photodetection and stable performance under bending conditions, which have never been achieved at the same time."

The discovery is detailed in the journal Advanced Optic Materials.

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