JST Create Enterprise of Future Society �@ New Technology Presentation Meeting
The latest research results of electrochromic modulated light glass and organic film solar cell were reported

May 13, "JST Create Enterprise of Future Society �@ New Technology Presentation Meeting" was held by online method. In this here, two oral presentations about electrochromic modulated light glass and organic film solar cell are picked up.

EC modulated light glass is driven at ultra-low voltage by use of new EC material

Mr.Higuchi of National Institute for Materials Science (NIMS) reported that electrochromic (EC) modulated light glass could be driven at mere 0.8 V by making use of new EC material.

Fig.1 EC change of ultra-high molecular polymers and its color variation

As you know, EC device has been practical use for window of airplane and antidazzle mirror of automobile. However, in the conventional device, Wo3 or viologen are used as an EC material, as a result, its's difficult to correspond to large substrate and cost reduction. Therefore, the research group developed metallosupramolecular polymers as new EC materials, was possible to be coated.

Figure 1 shows typical molecular structure. Various colors are gained by kind of metallic species and organic polymers. And also, color changes greatly due to minimum electric quantity. Of course, it's easy to correspond to plastic film substrate. As above, it could be driven at low voltage same as 08 V by optimization of device structure and EC material. Furthermore, after coloring, coloring state keeps at voltage off. For this reason, if it's used as window, light shielding state keeps without voltage.

IPCE of organic film solar cell was increased to 16 %

On the other hand, Prof.Osaka of Hiroshima University reported an originally organic film solar cell, which was produced by printing process, and then, device with high efficiency was developed by use of organic semiconductor polymer with sufficient solubility.

In the past, the research group synthesized PNTz4T as p-type material of fullerene type device. High incident photon-to-current efficiency (IPCE) of pilot-produced device was obtained same as 10.1 % due to high crystallizability and carrier mobility. However, its solubility against solvent was insufficient, so that, it was necessary to anneal at approximate 100 ℃ due to preparation of polymer liquid.

Therefore, the research group PTNT2T with rigid molecular structure. As a result, its solubility was sufficient such as 8g/L at R.T. And also, IPCE of this device was approximate 12 %, was world's largest as fullerene series device.

Furthermore, if Y6 as n-type non-fullerene polymer and PNBTz1 or PTBTz2 as p-type polymer are used, ICPE was increased 12 % from max.16 % while keeping sufficient solubility.

Fig.2 Molecular structure and absorption wavelength of polymer material

Fig.3 Molecular structure of PNBTz1 and PTBTz2, their device characteristics