Thin and Flexible Organic Photovoltaic Devices Engineered to Resist Both Mechanical and Thermal Stress

Figure 1: Photograph of 3-micrometer-thick organic solar cell that was adhered to fabric by an instantaneous hot-melt procedure.

Reproduced from Ref 1. with consent from PNAS © 2018

A flexible polymer-based solar cell that can be warmed up to 120 degrees Celsius without minimizing its capability to harvest energy has actually been established by a group led by RIKEN researchers1. The mix of versatility and thermal toughness makes it appealing for powering wearable sensing units and devices.

Organic solar batteries utilize conductive, carbon-based polymers rather of stiff silicon to capture sunshine and transform it into electrical energy. They can hence be connected to irregular supports such as clothes without breaking.

Previously,Kenjiro Fukuda of the RIKEN Center for Emergent Matter Science and his group had actually encapsulated organic solar batteries in other polymers to enhance their compatibility with fabrics by making them harder and more water resistant.

However, one issue that still restricts the long-lasting life time of flexible solar batteries is their bad resistance to temperature level modifications. Thermal stress can make polymers fragile or trigger them to end up being less conductive through growth.

Fukuda, with group leader Takao Someya and associates from Japan and the United States, conquered this issue and made organic solar batteries with boosted thermal stability by customizing the gadget’s active layer– a complex, light-absorbing polymer made up of fluorine atoms and sulfur-containing fragrant rings. Adding direct hydrocarbon chains to this particle set off the fragrant rings to stack in a ‘face-on’ orientation that improved the polymer’s crystal strength.

The group changed the traditional plastic substrates utilized to support the active layer with transparent polyimides that are mechanically steady over a broad temperature level variety. To form the polyimide movie on a supporting plate, they utilized a wet-chemistry procedure, instead of vacuum deposition, given that it is more open for producing large-area movies.

But a wet-chemistry procedure requires thoroughly managing the substrate’s surface area energy: if the substrate is too hydrophobic, the polyimide precursor service will bead and not form a movie, whereas if it is too hydrophilic, the polyimide movie will adhere too highly, making it tough to peel. The scientists accomplished the best surface area energy by changing the density of a hydrophobic layer and treating it with oxygen plasma.

Following a last encapsulation action, they evaluated the habits of their solar cell as it was rolled, folded, and folded consistently at various temperature levels. The power conversion performances stayed at near-record rates regardless of the mechanical and thermal stress. This motivated the group to connect the devices to materials utilizing ‘hot-melt’ technology established for the fashion industry.

“The hot-melt process gives almost perfect adhesion of our ultrathin organic solar cells onto textiles, with no degradation in performance,” statesFukuda “We’re now discussing these results with our collaborators to find a good strategy for commercialization.”

Source: RIKEN

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