Solar cells are converters that make electricity out of light energy by the photovoltaic effect. Made with organic semiconductors, organic solar cells are light and flexible, can produce electricity with a small amount of sunlight, and can be manufactured at a low cost. As a result, they are suitable for products that need self-generated electricity such as solar windows or certain military products rather than for solar power plants.

In Angewandte Chemie, a renowned journal for the field of chemistry, a POSTECH master’s student published a paper on a new manufacturing technology for organic solar cells which can significantly increase their lifetime.

Under the supervision of Professor Tae Woo Lee of Department of Materials Science and Engineering, Ms. Mi-Ri Choi developed the new technology by introducing self-doped conducting polymer compositions for Organic Light Emitting Diodes (OLEDs) and organic solar cells. The team estimates that the new technology will increase the current lifetime of the cells by about 38 times.

The research capitalizes on the water-soluble characteristic of self-doped conducting polymer compositions. While the selfdoped compositions maintain their form when made into films, the existing compositions do not dissolve but disperse in water; therefore it is difficult to have them evenly spread without defects when making films.

Also, the team added perfluorinated ionomers to the composition in order to make it build the surface layer by selforganization. This remedies the shortcomings of the existing materials nicely, for the work function – the minimal work or energy needed to pull one electron outside a substance – could hardly be manipulated. As a result, it was difficult to both inject/extract holes into/from the organic semiconducting layers.

By applying the concept above to the hole injection and extraction layers of OLEDs and organic solar cells, the team successfully increased the luminescence and lifetime substantially. Specialists expect that this new approach will contribute to OLED development of more effective displays and Professor Tae-Woo Lee commented, “Organic electronic devices are an important research topic whose future application will be extended to various fields. It is remarkable that a master’s program student produced such an achievement.”

The team collaborated with Cheil Industries, a Samsung affiliate that produces electronic materials.