Technology – Organic Electronic Materials

Organic electronics, plastic electronics or polymer electronics, is a branch of materials science dealing with electrically-conductive polymers and conductive small molecules. It is called ‘organic’ electronics because the polymers and small molecules are carbon-based. This contrasts with traditional electronics, which relies on inorganic conductors and semiconductors, such as copper and silicon, respectively. Polymer Electronics is expected to become one of the key technologies in the 21st century. Semiconducting polymers are predicted to become the semiconducting material of this century, gaining a comparable share on the market as Si based technology gained during the previous century. Conjugated polymers exhibit a great variety of technologically relevant properties as for example absorption and emission of light or electrical and photoconductivity, thus making them useful materials for the application in electronic devices.

Organic (conjugated) polymers typically offer the advantage that they are light-weight and flexible materials which can be processed from solution by spin coating or inkjet printing at room temperature. Especially, conjugated polymers as electron donor and acceptor components in organic photovoltaic applications are of interest owing to the possibility of attaining multiple redox states (p-type or n-type doping) in a small potential window. This is due to the placement of the valence band relative to the conduction band. By using electron-rich or electron deficient building blocks of various strengths one can control the magnitude of the polymer band gap and the relative position of the energy levels. This makes them promising for the production at low cost and for large-area employments in other electronic applications such as supercapacitors, ambipolar field-effect transistors, solar cells, light-emitting devices and electrochromic devices.

Significant revolution in the chemistry and molecular engineering of conjugated polymers has been witnessed by the increased demand for novel electron donor conjugated polymers in the area of organic photovoltaics (OPVs). New electron donor conjugated polymers were developed that when blended with [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) fullerene derivative, significant improvements in device performance has been observed. For example, power conversion efficiencies (PCEs) of 10%, based on blends of conjugated polymers as electron donors and soluble fullerene derivatives, especially PC61BM or [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as electron acceptors, have been presented. Some of the state-of-the-art electron donor conjugated polymers are presented on the Schemes and photos on the right and below.