Free Newsletters - Space - Defense - Environment - Energy - Solar - Nuclear
..
. Space Industry and Business News .




CHIP TECH
Organic nanowires open the way for optoelectronic device miniaturization
by Eunhee Song
Seoul, Korea (SPX) Mar 15, 2013


Schematic diagram of single-crystalline nanowire organic phototransistors. Copyright Wiley-VCH Verlag GmbH and Co. KGaA.

Research team of Ulsan National Institute of Science and Technology (UNIST), Ulsan, South Korea, developed high-performance organic phototransistors (OPTs) based on single-crystalline n-channel organic nanowires.

Phototransistors are a kind of transistors in which the incident light intensity can modulate the charge-carrier density in the channel.

Compared with conventional photodiodes, phototransistors enable easier control of light-detection sensitivity without problems such as the noise increment. However, to date, the research has mostly focused on thin-film OPTs, and nanoscale OPTs have scarcely been reported.

OPTs have many intrinsic advantages over their inorganic counterparts, such as the chemical tunability of optoelectronic properties by molecular design and high potential in low cost, light-weight, flexible applications.

Single-crystalline nano-/microwires (NWs/MWs) based on organic semiconductors have attracted great interest recently as they are promising building blocks for various electronic and optoelectronic applications. In particular, OPTs based on single-crystalline NWs/MWs may yield higher light sensitivity than their bulk counterparts.

In addition, their one-dimensional, intrinsically defect-free and highly ordered nature will allow a deeper understanding of the fundamental mechanisms of charge generation and transport in OPTs, while enabling a bottom-up fabrication of optoelectronic nanodevices

Prof. Joon Hak Oh and Hojeong Yu, working at UNIST, together with Prof. Zhenan Bao at Stanford University, USA, have worked on n-channel single-crystalline nanowire organic phototransistors (NW-OPTs) and observed significant enhancement in the charge-carrier mobility of NW-OPTs.

Prof. Oh said, "The development of OPTs based on n-channel single-crystalline organic semiconducting NWs/MWs is highly desirable for the bottom-up fabrication of complementary metal oxide semiconductor (CMOS)-like photoelectronic circuits, which provides various advantages such as high operational stability, easy control of photoswitching voltages, high photosensitivity and responsivity."

The photoelectronic characteristics of the single-crystalline NW-OPTs such as the photoresponsivity, the photo-switching ratio, and the photoconductive gain, were analyzed from the I-V characteristics coupled with light irradiation and compared with those of vacuum-deposited thin-film devices.

The external quantum efficiencies (EQEs) were also investigated for the NW-OPTs and thin-film OPTs. In addition, they calculated the charge accumulation and release rates from deep traps, and investigated the effects of incident light intensity on their photoelectronic properties.

A mobility enhancement is observed when the incident optical power density increases and the wavelength of the light source matches the light-absorption range of the photoactive material.

The photoswitching ratio is strongly dependent upon the incident optical power density, whereas the photoresponsivity is more dependent on matching the light-source wavelength with the maximum absorption range of the photoactive material.

NW-OPTs based on n-channel semiconductor, N,N '-bis(2-phenylethyl)-perylene-3,4:9,10-tetracarboxylic diimide (BPE-PTCDI), exhibited much higher external quantum efficiency (EQE) values ("7900 times larger) than thin-film OPTs, with a maximum EQE of 263 000%.

This phenomena result from the intrinsically defect-free single-crystalline nature of the BPE-PTCDI NWs. In addition, an approach was devised to analyze the charge-transport behaviors using charge accumulation/release rates from deep traps under on/off switching of external light sources.

"Our approach to charge-accumulation/release-rate calculations could provide a fundamental understanding about charge-carrier-density variations under light irradiation, which subsequently enables in-depth study of OPTs," said Prof. Oh,

"Hence organic single-crystalline NW-OPTs are a highly promising alternative to conventional thin-film-type photodiodes, and can effectively pave the way for optoelectronic device miniaturization."

This research was supported by a National Research Foundation of Korea (NRF) Grant funded by the Ministry of Education, Science, and Technology (MEST), and the Global Frontier Research Center for Advanced Soft Electronics and published in Advanced Functional Materials (Title: High-Performance Phototransistors Based on Single-Crystalline n-Channel Organic Nanowires and Photogenerated Charge-Carrier Behaviors, 5 Feb 2013).

The article can be found here.

.


Related Links
Ulsan National Institute of Science and Technology
Computer Chip Architecture, Technology and Manufacture
Nano Technology News From SpaceMart.com






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





CHIP TECH
Ultra-high-speed optical communications link sets new power efficiency record
Washington DC (SPX) Mar 15, 2013
Ultrafast supercomputers that operate at speeds 100 times faster than current systems are now one step closer to reality. A team of IBM researchers working on a U.S. Defense Advanced Research Projects Agency (DARPA)-funded program have found a way to transmit massive amounts of data with unprecedentedly low power consumption. The team will describe their prototype optical link, which shatt ... read more


CHIP TECH
Mobile LIDAR technology expanding rapidly

First Laser Communication System Integrated, Ready for Launch

Earth will drown in garbage

Raytheon's dual-band datalink tested with Thales radar

CHIP TECH
DoD Selects Northrop Grumman for Joint Command and Control System

Northrop Grumman Highlights Affordable Milspace Communications

Boeing Ships 5th WGS Satellite to Cape Canaveral for 2013 Launch

INTEROP-7000 uses ISSI to link IP-based voice comms with legacy radio

CHIP TECH
Vega receives its upper stage as the next mission's two primary passengers land in French Guiana

Grasshopper Successfully Completes 80M Hover Slam

Musk: 'I'd like to die on Mars'

Ariane 5 vehicle for next ATV resupply mission in Kourou

CHIP TECH
Galileo fixes Europe's position in history

China city searching for 'modern Marco Polo'

Milestone for European navigation system

China targeting navigation system's global coverage by 2020

CHIP TECH
Air Force overrides Beechcraft LAS protest

Boeing Says Strong Demand Pushing Commercial Production Rates Higher

As F-35 costs soar, Boeing enters the fray

Boeing, KLM Demonstrate New Technologies to Optimize Flight

CHIP TECH
Surprising Control over Photoelectrons from a Topological Insulator

Organic nanowires open the way for optoelectronic device miniaturization

Ultra-high-speed optical communications link sets new power efficiency record

New distance record for 400 Gb/s data transmission

CHIP TECH
Google Maps adds view from Mt. Everest

Significant reduction in temperature and vegetation seasonality over northern latitudes

GOCE: the first seismometer in orbit

Japan's huge quake heard from space: study

CHIP TECH
China to more than double air monitoring network

Little faith in China leaders' pollution promises

Dead pigs contaminating Chinese river?

Toxic gas leak in South Korea, 11 hospitalised




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement