PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

High-performance, NW-OPTs open the way for optoelectronic device miniaturization

2013-03-13
(Press-News.org) 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 at http://onlinelibrary.wiley.com/doi/10.1002/adfm.201201848/abstract


ELSE PRESS RELEASES FROM THIS DATE:

Social networking policies may violate employee rights, NLRB finds

2013-03-13
Social networking policies may violate employee rights, NLRB finds Article provided by Bryan E. Kuhn, Counselor at Law, P.C. Visit us at http://www.bryankuhnlaw.com In the Internet era, social networking sites like Twitter and Facebook have largely replaced the proverbial workplace water cooler. Unlike old-fashioned chatter between coworkers, however, an employee's gripes and grievances can easily become both public and permanent when aired online. To address this issue, many businesses have sought ways to safeguard their online reputations by creating policies ...

Texas Boy's Forearm Amputated After Washing Machine Accident

2013-03-13
Texas Boy's Forearm Amputated After Washing Machine Accident Article provided by Portner & Bond, PLLC Visit us at http://www.portnerbond.com/ An eight-year-old Texas boy wanted his Spider-Man bed sheets, which were in the washing machine. He left his bedroom, went into the garage and opened up the washing machine to take them out; the agitator stopped spinning when he lifted the lid as it was supposed to. But when he reached inside, it started spinning again, according to the El Paso Times. As a result, he lost his forearm. Defective-Product Lawsuits Catastrophic ...

Which type of bankruptcy is right for you?

2013-03-13
Which type of bankruptcy is right for you? Article provided by The Law Offices of Raymond J. Antonacci, LLC Visit us at http://www.rjalegal.com If you are considering bankruptcy, you typically have two different options to choose from: Chapter 7 and Chapter 13. You may have questions about which option is right for you. The answer: it depends on your personal situation. In both types of bankruptcy, you eventually are granted a discharge, meaning that you no longer have to pay many of your outstanding debts. However, that is where the similarities end for the ...

Child custody and visitation in Michigan

2013-03-13
Child custody and visitation in Michigan Article provided by Law Office of Michael A. Robbins, PLLC Visit us at http://www.michaelarobbins.com Michigan couples considering a divorce have a lot to think about. Thinking about divorce is even more complicated when children are involved. Michigan child custody laws are in place to protect children and help create a post-divorce setting that is best for them. Types of child custody in Michigan In Michigan there is both physical custody and legal custody. Physical custody refers to where the child will actually ...

Possible changes to DWI laws in North Carolina

2013-03-13
Possible changes to DWI laws in North Carolina Article provided by Barnett & Falls Visit us at http://www.barnettfalls.com Several recent proposals under consideration at the North Carolina legislature would increase penalties for first time and repeat DWI offenders. The changes are part of a pattern to stiffen DWIpenalties in the state. The first bill changes the definition of habitual offender. Under current law, a DWI habitual offender is someone charged with four DWIs in a ten-year period. The habitual offender charge is a felony. Penalties for a Class ...

OMG! California proposes tougher distracted driving laws for teens

2013-03-13
OMG! California proposes tougher distracted driving laws for teens Article provided by Law Office of Daniel J. O'Neill Visit us at http://www.danieljoneill.com Because of the danger that distracted drivers, particularly those in the teenage years cause, many states have passed laws banning activities ranging from texting or using hand-held cellphones while behind the wheel. In California, it is illegal for drivers younger than 18 to use a cellphone (hand-held or hands-free) while behind the wheel. Additionally, there is a statewide ban on texting while driving for ...

Statistics show traffic fatalities rising in the US

2013-03-13
Statistics show traffic fatalities rising in the US Article provided by Schuster Jachetti LLP Visit us at http://www.mydelawarelawyer.com/ Every year since 2005, the number of fatalities caused by motor vehicle accidents has declined -- until 2012. According to data released by the National Safety Council, a non-profit organization, more people were killed in auto accidents in 2012 than the year prior. The NSC reported that approximately 36,200 people were killed in motor vehicle crashes in 2012, representing a 5 percent increase from the year before. The NSC ...

Fiscal-cliff law settles federal estate tax for now

2013-03-13
Fiscal-cliff law settles federal estate tax for now Article provided by The Haley Law Group, LLC Visit us at http://www.haleylawgroup.com Estate and tax planning have been complicated in the past decade or so by the fluctuating and uncertain federal estate tax. Thanks to last-minute action by Congress and President Obama, the top federal estate tax rate is set at 40 percent going forward on estates over $5 million. Adjusted for inflation, the first $5.25 million in estate assets will be exempt from federal estate tax for those dying in 2013. Estate taxes An ...

Does Michigan need stricter distracted driving laws?

2013-03-13
Does Michigan need stricter distracted driving laws? Article provided by MATZ & PIETSCH PC Visit us at http://www.matzandpietsch.com In the age of cellphone addiction, distracted drivers have become a common phenomenon on our roadways -- often leading to serious motor vehicle accidents. In 2011, the National Highway Traffic Safety Administration reported that 3,331 people lost their lives in distracted driving accidents across the country. In addition, approximately 387,000 people sustained personal injuries in such crashes that year. To prevent these dangerous ...

Resolving workers' compensation disputes through a formal claim petition

2013-03-13
Resolving workers' compensation disputes through a formal claim petition Article provided by Kaplan & Kaplan Counselors at Law Visit us at http://www.workerscompensationlawyersnj.com People who are injured on the job or who acquire an illness or disease through their work do not have to prove fault by their employers to receive compensation for their medical care and related expenses. Certain requirements still apply, though, and workers must demonstrate that the injury or illness was caused or aggravated by a work act, exposure or accident that occurred in ...

LAST 30 PRESS RELEASES:

Printed skin to replace animal testing

Precision medicine could be possible in the fight against antibiotic resistance

Researchers at the Lewis Katz School of Medicine at Temple University identify new targeted approach to protect neurons against degeneration

Western diet causes inflammation, traditional African food protects

Electrochemical method supports nitrogen circular economy

How researchers are shining a light on kidney disease

Some gut bacteria could make certain drugs less effective

PEPITEM sequence shows effects in psoriasis, comparable to steroid cream

Older teens who start vaping post-high school risk rapid progress to frequent use

Corpse flowers are threatened by spotty recordkeeping

Riding the AI wave toward rapid, precise ocean simulations

Are lifetimes of big appliances really shrinking?

Pink skies

Monkeys are world’s best yodellers - new research

Key differences between visual- and memory-led Alzheimer’s discovered

% weight loss targets in obesity management – is this the wrong objective?

An app can change how you see yourself at work

NYC speed cameras take six months to change driver behavior, effects vary by neighborhood, new study reveals

New research shows that propaganda is on the rise in China

Even the richest Americans face shorter lifespans than their European counterparts, study finds

Novel genes linked to rare childhood diarrhea

New computer model reveals how Bronze Age Scandinavians could have crossed the sea

Novel point-of-care technology delivers accurate HIV results in minutes

Researchers reveal key brain differences to explain why Ritalin helps improve focus in some more than others

Study finds nearly five-fold increase in hospitalizations for common cause of stroke

Study reveals how alcohol abuse damages cognition

Medicinal cannabis is linked to long-term benefits in health-related quality of life

Microplastics detected in cat placentas and fetuses during early pregnancy

Ancient amphibians as big as alligators died in mass mortality event in Triassic Wyoming

Scientists uncover the first clear evidence of air sacs in the fossilized bones of alvarezsaurian dinosaurs: the "hollow bones" which help modern day birds to fly

[Press-News.org] High-performance, NW-OPTs open the way for optoelectronic device miniaturization