Organic solar cell attached to clothes and it is “washable”

A Japanese research group has developed a stretchable, waterproof ultra-thin organic solar cell that can be attached to clothes and washed.

The group was jointly formed by Riken, Japan Science and Technology Agency (JST) and the University of Tokyo. The solar cell is expected to be used as a power source that is for wearable devices and e-textiles and stable for a long period of time.

For the development of wearable sensors targeted at “biological continuous monitoring” (continuous monitoring of biological data such as blood pressure and body temperature), a power source that can be attached to clothes is necessary. Organic solar cells are drawing attention as major candidates because they can supply more than 1mW of power and are flexible.

On the other hand, it is necessary to realize a high enough energy conversion efficiency, flexibility and water resistance at the same time, which has so far been difficult. Especially, with a very thin film, a flat film surface cannot be easily realized. And it is difficult to stably operate such a cell while keeping a high performance for a long period of time because of the drastic deterioration of gas barrier property.

This time, by using the PNTz4T semiconducting polymer, which Riken developed in 2012, the research group formed an organic solar cell with a reversed structure, which realizes an excellent environmental stability, on a parylene substrate (1μm-thick polymer material).

With the solar cell detached from a glass supporting substrate, the group realized an energy conversion efficiency of 7.9%. At the time of emitting pseudo sunlight (output: 100mW/cm2), it has a short-circuit current density (JSC) of 16.2mA/cm2, release voltage (VOC) of 0.71V and fill factor of 69%.

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