Featured Research

from universities, journals, and other organizations

Electrostatics do the trick: Simple model describes what happens between organic semiconductors and metals

Date:
June 23, 2014
Source:
Helmholtz-Zentrum Berlin für Materialien und Energie
Summary:
Organic semiconductors allow for flexible displays, solar cells, and other applications. One common problem in these devices, however, is the interface between the metallic contacts and the organic semiconductor material, where undesirable losses occur. Now researchers have shown what these losses depend upon.

When inserting an ultrathin dielectric between metal electrode and organic semiconductor, charge carriers (shown here for a positively charged holes in red) are, counter intuitively, more efficiently extracted from their transport level (blue) in the organic to the Fermi level (black) in the metal than without the interlayer.
Credit: M Oehzelt/HZB

Organic semiconductors allow for flexible displays (OLEDs), solar cells (OPVCs), and other interesting applications. One common problem in these devices, however, is the interface between the metallic contacts and the organic semiconductor material, where undesirable losses occur. Now Dr. Martin Oehzelt has shown what these losses between the metal and the organic semiconductors depend upon and how to minimize them. In particular, his model also explains why a thin, electrically insulating layer between the two materials can even facilitate the transition of charge carriers. His results have recently been published in Nature Communications.

Currently, there are many different approaches describing the interface between organic semiconductor materials and metallic contacts. These somewhat contradictory theories, none of which is universally valid for all cases, have now been unified by Oehzelt and developed into a single coherent model based on the electrostatic potential caused by the charge carriers in the metal and the organic semiconductor. "I calculated the impact of the charge carrier distribution on the electronic states at the interface and how these changes feed back onto the charge carrier distribution," he explains. Oehzelt is presently conducting research with Dr. Georg Heimel as a postdoc for Prof. Norbert Koch, who works at the Humboldt-Universität zu Berlin and the Helmholtz-Zentrum Berlin.

Such calculations have never been so comprehensively carried out before. Performing them, Oehzelt states: "it was surprising to me that the quantum physical level was not that important. The electrostatic effects predominated! The agreement between our model and the experimental data were astonishing." On the example of pentacene, a common organic semiconductor, Oehzelt has quantitatively checked the model's predictions for interface losses. The energy distribution of the electronic states in organic semiconductors determines the minimum energy barrier the charge carriers have to overcome in transitioning from or into the metal. The calculation demonstrates that the shape of this energy barrier can vary, from a step-function to slow, continuously rising curves that lead to considerably lower losses. The latter can be achieved by introducing an extremely thin insulating layer between the organic semiconductor and the metal. Contrary to the general expectation, the introduction of an insulator thus improves the electrical contact.

The results of this work could notably simplify optimization of interfaces and contacts and, thereby, the development of more efficient organic electronic devices.


Story Source:

The above story is based on materials provided by Helmholtz-Zentrum Berlin für Materialien und Energie. Note: Materials may be edited for content and length.


Journal Reference:

  1. Martin Oehzelt, Norbert Koch, Georg Heimel. Organic semiconductor density of states controls the energy level alignment at electrode interfaces. Nature Communications, 2014; 5 DOI: 10.1038/ncomms5174

Cite This Page:

Helmholtz-Zentrum Berlin für Materialien und Energie. "Electrostatics do the trick: Simple model describes what happens between organic semiconductors and metals." ScienceDaily. ScienceDaily, 23 June 2014. <www.sciencedaily.com/releases/2014/06/140623104257.htm>.
Helmholtz-Zentrum Berlin für Materialien und Energie. (2014, June 23). Electrostatics do the trick: Simple model describes what happens between organic semiconductors and metals. ScienceDaily. Retrieved August 22, 2014 from www.sciencedaily.com/releases/2014/06/140623104257.htm
Helmholtz-Zentrum Berlin für Materialien und Energie. "Electrostatics do the trick: Simple model describes what happens between organic semiconductors and metals." ScienceDaily. www.sciencedaily.com/releases/2014/06/140623104257.htm (accessed August 22, 2014).

Share This




More Matter & Energy News

Friday, August 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Former TSA X-Ray Scanners Easily Tricked To Miss Weapons

Former TSA X-Ray Scanners Easily Tricked To Miss Weapons

Newsy (Aug. 21, 2014) — Researchers found the scanners could be duped simply by placing a weapon off to the side of the body or encasing it under a plastic shield. Video provided by Newsy
Powered by NewsLook.com
Flower Power! Dandelions Make Car Tires?

Flower Power! Dandelions Make Car Tires?

Reuters - Business Video Online (Aug. 20, 2014) — Forget rolling on rubber, could car drivers soon be traveling on tires made from dandelions? Teams of scientists are racing to breed a type of the yellow flower whose taproot has a milky fluid with tire-grade rubber particles in it. As Joanna Partridge reports, global tire makers are investing millions in research into a new tire source. Video provided by Reuters
Powered by NewsLook.com
Awesome New Camouflage Sheet Was Inspired By Octopus Skin

Awesome New Camouflage Sheet Was Inspired By Octopus Skin

Newsy (Aug. 19, 2014) — Scientists have developed a new device that mimics the way octopuses blend in with their surroundings to hide from dangerous predators. Video provided by Newsy
Powered by NewsLook.com
Researcher Testing on-Field Concussion Scanners

Researcher Testing on-Field Concussion Scanners

AP (Aug. 19, 2014) — Four Texas high school football programs are trying out an experimental system designed to diagnose concussions on the field. The technology is in response to growing concern over head trauma in America's most watched sport. (Aug. 19) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins