World Record Efficiency for Small Organic Photovoltaic Cells

Published on 03/23/2020

After six months of cooperative research, Japanese chemical specialist Toyobo Co. and CEA succeeded in manufacturing small organic photovoltaic (PVO) cells on a glass substrate that achieved the world's best conversion efficiency(1) in a dark room. Toyobo wants to make this material the wireless power source for the Internet of things, like temperature-humidity and motion sensors.

Toyobo has developed an energy-generating material specific to PVO to produce high power from light sources in low-light rooms, using organic synthesis technologies that the company has cultivated during its years of research in fine chemistry(2). The material can dissolve easily, even in halogen-free solvents, allowing it to be uniformly applied to a substrate and produce energy stably with few individual differences. 

In order to put the material into practice as quickly as possible, Toyobo has been conducting joint research with CEA-Liten for six months at INES since June 2019. During this collaboration, Toyobo and CEA succeeded in manufacturing small PVO cells on a glass substrate with the best conversion efficiency in the world by optimizing the solvents and the coating technique. In a verification experiment under 220 lux neon light, equivalent to the brightness of a darkroom, it was confirmed that the product under test achieved a conversion efficiency of approximately 25%, 60% higher(3) than the amorphous silicon solar cells commonly used in desktop calculators. Although it is more complex to apply an energy-generating material to a PET film than to a glass substrate, the teams also developed prototype PVO modules on a PET film substrate with an effective area of 18 square centimeters. The module was capable of producing approximately 130 microwatts under the same illumination.

Toyobo plans to offer this material to solar cell manufacturers in particular, based on the know-how gained from this joint research. The aim is for the material to be used by March 2023 primarily as a wireless power source for temperature-humidity and motion sensors. 

The PVO cell is a solar cell, which is created by coating organic energy-generating materials, such as carbon and sulfur atoms, with electrodes on a glass or plastic substrate. Because the PVO cell is very thin and flexible, it attaches easily to walls or fabric surfaces where common inorganic solar cells cannot be installed. As a result, there are high expectations for PVO as a wireless power source for sensors and portable devices, which are indispensable for the Internet of Things (IoT). 

(1) According to Toyobo's research as of March 23, 2020.
(2) According to Toyobo's press release of July 31, 2019.
(3) Compared to a conversion efficiency of 16% for general solar cells in amorphous silicon, measured by Toyobo under a brightness of 220 lux. 

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