Research Highlights

Setting energy levels too high to catch electrons

Published online 5 August 2012

Designing new semiconductor polymers may overcome the inefficiency caused by "charge traps".

Hazem Zohny

Plastic semiconductors offer the prospect of cheap, mass-produced electronics such as polymer light-emitting diodes (LEDs) and solar cells. However, in practice, an electronic phenomenon know as "charge traps", in which electrons are caught in the material's electronic circuit, is reducing the efficiency of devices and limiting the technology.

An international team of researchers investigated these traps, proposing a theoretical framework for designing trap-free plastic electronics, publishing their results in Nature Materials.

They compared nine different plastic polymers and found that the distribution of traps and their energy levels were similar in all the materials investigated. This similarity might make it possible to predict the electron current in different plastic semiconductors.

Quantum-chemical calculations conducted by the researchers suggest that these energy levels reflect what would be expected if hydrated oxygen complexes were causing the traps. Previous research has suggested that the traps are caused by kinks in the polymer chains or impurities in the material. The researchers add that such hydrated oxygen complexes could easily contaminate polymer semiconductors during the manufacturing process.

With further research, these findings may help chemists design semiconducting polymers in which the energy levels of traps are set higher than that of electrons flowing through the material. This would allow electrons to flow unhindered, thereby maximizing the current and increasing the efficiency of devices that include semiconducting polymers.


  1. Nicolai, H.T. et al. Unification of trap-limited electron transport in semiconducting polymers. Nature Materials doi:10.1038/nmat3384 (2012)