[스크랩] 자랑스런 한국인 박사 [무지개빛 태양전지 에너지] 논문발표

 

태양전지도 이제 '하이브리드'

까맣던 태양전지, 무지개색 입는다

미국 미시간대, 이재용-이규태-서성용 연구원..태양전지 두께 최소화

검은색 일색인 태양전지가 무지개색을 입는다.

태양전지에 원하는 색을 입히는 기술이 한국 과학자들이 참여한 연구팀에 의해 개발됐다.

미국 미시간대학교 이재용, 이규태, 서성용 연구원은 지도교수인 제이 구오(L. Jay Guo) 교수와 함께 투명하면서도 다양한 색과 패턴을 갖는 태양전지를 주제로 한 논문을 세계적인 과학학술저널 네이쳐지의 자매지인 <사이언티픽 리포트>에 지난달 28일 발표했다고 5일 밝혔다.

이로써 검은색 일색으로 오로지 건물 '옥상'에만 숨어있어야 했던 태양전지가 이제 건물 내·외벽 등에 자유로운 외출을 시도할 수 있게 됐다.

 

검은색 태양전지에 다양한 색을 입히는 원리는 간단
실리콘층에서 일어나는 공진현상을 이용해 원하는 파장의 빛만 투과시키는 것이다.
예를 들어 실리콘 층의 두께를 얇게 하면 파란색이, 두껍게 하면 빨간색이 되는 것이다.

태양전지는 반도체를 이용해 태양빛의 에너지를 전기에너지로 바꾸는 전지다.
태양 입자가 실리콘 태양전지에 흡수되면 전자(electron)와 전공(hole)이 발생하는데, 빛이 실리콘에 닿으면 전자가 튀어나와 N형으로 향하고 이때 N형에서 P형으로 전류가 흐른다.

기존 태양전지는 반도체의 PN 접합을 사용한 실리콘 태양전지가 주로 사용됐지만 연구팀은 여기에서 'PN 도핑층'을 완전히 제거했다. P도핑층 대신 전공 전도도가 좋은 무기 물질층을 사용했고, N도핑층 대신 전자 전도도가 뛰어난 유기 물질층을 적용한 것이다.

전공과 전자를 선택적으로 양쪽 전극으로 효율적으로 빼낼 수 있어 연구팀은 이를 '하이브리드형'이라고 이름을 붙였다. 이재용 연구원은 "태양에너지로 생성된 전기 입자들의 손실을 거의 완벽하게 제거하고 모두 전기에너지로 변환할 수 있다"고 설명했다.

이를 통해 연구팀은 태양전지의 두께를 6나노미터(㎚, 10억분의 1ｍ)로 줄였다.
기존에 쓰이던 것(300나노미터)보다 1/50로 얇아진 것으로 세계 최초다.

연구팀은 "대면적 디스플레이를 제작하는 장비를 이용할 수 있다면 바로 LCD TV 크기의 태양전지를 만들 수 있다"며 "기업들과 함께 협력한다면 1년 내에 대면적 하이브리드형 제품이 나올 것"이라고 내다봤다.

 

 

※ Transparent color solar cells fuse energy, beauty

☞ http://eecs.umich.edu/eecs/about/articles/2014/guo-transparent-color-solar-cells-fuse-energy-beauty.html

△ (왼쪽부터) 이재용, 이규태, 서성용 연구원 ⓒ 연구팀 제공

 

 

Transparent color solar cells fuse energy, beauty

 

March 3, 2014
Nicole Casal Moore

ANN ARBOR, Mich. - Colorful, see-through solar cells invented at the University of Michigan could one day be used to make stained-glass windows, decorations and even shades that turn the sun's energy into electricity.

The cells, believed to be the first semi-transparent, colored photovoltaics, have the potential to vastly broaden the use of the energy source, says Jay Guo, a professor of electrical engineering and computer science, mechanical engineering, and macromolecular science and engineering at U-M. Guo is lead author of a paper about the work newly published online in Scientific Reports.

"I think this offers a very different way of utilizing solar technology rather than concentrating it in a small area," he said. "Today, solar panels are black and the only place you can put them on a building is the rooftop. And the rooftop of a typical high-rise is so tiny.

"We think we can make solar panels more beautiful—any color a designer wants. And we can vastly deploy these panels, even indoors."

Guo envisions them on the sides of buildings, as energy-harvesting billboards and as window shades—a thin layer on homes and cities. Such an approach, he says, could be especially attractive in densely populated cities.

In a palm-sized American flag slide, the team demonstrated the technology.

"All the red stripes, the blue background and so on—they are all working solar cells," Guo said.

The Stars and Stripes achieved 2 percent efficiency. A meter-square panel could generate enough electricity to power fluorescent light bulbs and small electronic gadgets, Guo says. State-of-the art organic cells in research labs are roughly 10 percent efficient.

The researchers are working to improve their numbers with new materials, but there will always be a tradeoff between beauty and utility in this case. Traditional black solar cells absorb all wavelengths of visible light. Guo's cells are designed to transmit, or—in other versions—reflect certain colors, so by nature they're kicking energy from those wavelengths back out to our eyes rather than converting it to electricity.

Unlike other color solar cells, Guo's don't rely on dyes or microstructures that can blur the image behind them. The cells are mechanically structured to transmit certain light wavelengths. To get different colors, they varied the thickness of the semiconductor layer of amorphous silicon in the cells. The blue regions are six nanometers thick while the red is 31 (the team also made green, but that color isn't in the flag).

Amorphous silicon is commonly used in screens on cell phones, laptops and large LCD screens, in addition to solar cells. They sandwiched an ultrathin sheet of it between two semi-transparent electrodes that could let light in and also carry away the electrical current.

One of these so-called charge transport layers is made of an organic material. This hybrid structure, a combination of both organic and inorganic components, lets the researchers make cells that are 10 times thinner than traditional amorphous silicon solar cells. The organic layer replaces a thick 'doped' region that would typically controls the flow of electricity.

The ultrathin, hybrid design helps the cells hold their color and leads to a nearly 100 percent quantum efficiency. Quantum efficiency is different from overall efficiency. It refers to the percentage of light particles the device catches that lead to electrical current in that charge transport layer. Solar cells can leak current after this point, but researchers strive for a high number.

The cells' hues don't change based on viewing angle, which is important for several reasons. It means manufacturers could lock in color for precise pictures or patterns. It's also a sign that the devices are soaking up the same amount of light regardless of where the sun is in the sky. Conventional solar panels pivot across the day to track rays.

"Solar energy is essentially inexhaustible, and it's the only energy source that can sustain us long-term," Guo said. "We have to figure out how to use as much of it as we can."

The paper is titled "Decorative power generating panels creating angle insensitive transmissive colors." The work was funded by the National Science Foundation.

출처 : 무진장 - 행운의 집

글쓴이 : 봄꽃미소 원글보기

메모 :