Touch screens owe their magic to an electrically conductive film that sits just below the surface. In most devices, this layer is made from a compound known as indium tin oxide (ITO), which is rigid, expensive to manufacture, and requires the rare metal indium. Now, researchers have created a cheap and flexible alternative to ITO that could not only lower costs for touch screens, solar cells, and smart windows, but also enable new classes of bendable, wearable electronics.
“The work … is both intellectually inspiring and technologically exciting,” said Jian Pei, an organic chemist at Peking University who was not involved in the work.
As you scroll through TikTok videos, ITO conducts an unseen electrical current beneath your fingertips. Each time you swipe or tap, your finger disrupts that current and your phone reads the resulting signal. Your favorite videos can shine right through the ITO layer, which is transparent in thin films. This blend of transparency and conductivity also makes ITO essential in solar cells, light-emitting diodes, and smart windows, which change color under electrical fields. But because of ITO’s shortcomings, materials scientists have for years sought carbon-based or organic alternatives. Organic electronics tend to be flexible, which could enable them to be integrated into clothing or contoured surfaces. Additionally, organic materials are derived from cheap and abundant sources such as oil, rather than rare earth metals.
However, many transparent organic conductors degrade when exposed to water, oxygen, or high temperatures, making them practically unusable in commercial products or industrial applications. Hopes are higher for a new conducting material called PBDF, first reported last year by chemist Huang Fei of South China University of Technology and colleagues. Not only is PBDF stable in air, but it is capable of zipping electrons around much faster than other transparent organic conductors, rivaling the conductive properties of stainless steel. Moreover, it can be printed onto flexible surfaces as an ink, a cheaper and faster method than applying ITO, which must be sputtered or deposited on a surface in a vacuum. But for PBDF to make its way into real-life products such as touch screens and solar cells, it needs to be easily synthesized at scale.
That’s the significance of the latest result, from Purdue University chemist Jianguo Mei and colleagues. They developed a new synthetic technique that uses water and air to stitch together PBDF’s bonds with the help of a copper-based catalyst. Achieving this type of reaction in ordinary air—as opposed to the nitrogen gas used by Huang—“was previously considered impossible,” Pei says. That relative simplicity could encourage companies to adopt PBDF.
Mei’s team also showed how PBDF can be transparent when sprayed onto a surface as a thin film. The films let more than 80% of light through, showing similar transparency to ITO. The films had three times the conductivity of Huang’s versions of PBDF, Mei and colleagues report this month in the Journal of the American Chemical Society.
“The work looks very exciting,” says Doojin Vak, a materials scientist who researches printable photovoltaics at Australia’s Commonwealth Scientific and Industrial Research Organisation. However, given the huge leaps in conductivity between different films, he questions the measurements and believes there may have been a flaw in the setup. “I’m not sure if I can trust the result,” he says.
Mei agrees the results seem unbelievable, but he trusts that the data will hold up to scrutiny. “We could not believe it,” he says of his team’s reaction after seeing the results. “We did everything we could, even looking for outside help to validate the information. The data we collected was very exciting and at the same time very concerning because that [degree of conductivity] hasn’t been realistic in the past.”
Simone Fabiano, a chemist at Linköping University, says PBDF “represents a significant breakthrough in the field.” However, he cautions that PBDF needs to undergo more testing to determine whether it can be commercially viable. Pei wants researchers to test PBDF at extreme conditions like those generated inside solar cells to see whether its performance holds up.
Looking forward, Mei plans to push the conductivity of PBDF even higher by getting rid of tiny defects in the material. He also wants to design a PBDF ink that’s even better for printing. If the material holds up to its initial promise, “PBDF has enormous commercial potential,” Fabiano says.
Touch screens owe their magic to an electrically conductive film that sits just below the surface. In most devices, this layer is made from a compound known as indium tin oxide (ITO), which is rigid, expensive to manufacture, and requires the rare metal indium. Now, researchers have created a cheap and flexible alternative to ITO that could not only lower costs for touch screens, solar cells, and smart windows, but also enable new classes of bendable, wearable electronics.
“The work … is both intellectually inspiring and technologically exciting,” said Jian Pei, an organic chemist at Peking University who was not involved in the work.
As you scroll through TikTok videos, ITO conducts an unseen electrical current beneath your fingertips. Each time you swipe or tap, your finger disrupts that current and your phone reads the resulting signal. Your favorite videos can shine right through the ITO layer, which is transparent in thin films. This blend of transparency and conductivity also makes ITO essential in solar cells, light-emitting diodes, and smart windows, which change color under electrical fields. But because of ITO’s shortcomings, materials scientists have for years sought carbon-based or organic alternatives. Organic electronics tend to be flexible, which could enable them to be integrated into clothing or contoured surfaces. Additionally, organic materials are derived from cheap and abundant sources such as oil, rather than rare earth metals.
However, many transparent organic conductors degrade when exposed to water, oxygen, or high temperatures, making them practically unusable in commercial products or industrial applications. Hopes are higher for a new conducting material called PBDF, first reported last year by chemist Huang Fei of South China University of Technology and colleagues. Not only is PBDF stable in air, but it is capable of zipping electrons around much faster than other transparent organic conductors, rivaling the conductive properties of stainless steel. Moreover, it can be printed onto flexible surfaces as an ink, a cheaper and faster method than applying ITO, which must be sputtered or deposited on a surface in a vacuum. But for PBDF to make its way into real-life products such as touch screens and solar cells, it needs to be easily synthesized at scale.
That’s the significance of the latest result, from Purdue University chemist Jianguo Mei and colleagues. They developed a new synthetic technique that uses water and air to stitch together PBDF’s bonds with the help of a copper-based catalyst. Achieving this type of reaction in ordinary air—as opposed to the nitrogen gas used by Huang—“was previously considered impossible,” Pei says. That relative simplicity could encourage companies to adopt PBDF.
Mei’s team also showed how PBDF can be transparent when sprayed onto a surface as a thin film. The films let more than 80% of light through, showing similar transparency to ITO. The films had three times the conductivity of Huang’s versions of PBDF, Mei and colleagues report this month in the Journal of the American Chemical Society.
“The work looks very exciting,” says Doojin Vak, a materials scientist who researches printable photovoltaics at Australia’s Commonwealth Scientific and Industrial Research Organisation. However, given the huge leaps in conductivity between different films, he questions the measurements and believes there may have been a flaw in the setup. “I’m not sure if I can trust the result,” he says.
Mei agrees the results seem unbelievable, but he trusts that the data will hold up to scrutiny. “We could not believe it,” he says of his team’s reaction after seeing the results. “We did everything we could, even looking for outside help to validate the information. The data we collected was very exciting and at the same time very concerning because that [degree of conductivity] hasn’t been realistic in the past.”
Simone Fabiano, a chemist at Linköping University, says PBDF “represents a significant breakthrough in the field.” However, he cautions that PBDF needs to undergo more testing to determine whether it can be commercially viable. Pei wants researchers to test PBDF at extreme conditions like those generated inside solar cells to see whether its performance holds up.
Looking forward, Mei plans to push the conductivity of PBDF even higher by getting rid of tiny defects in the material. He also wants to design a PBDF ink that’s even better for printing. If the material holds up to its initial promise, “PBDF has enormous commercial potential,” Fabiano says.