Thursday, April 24, 2014
YOLO COUNTY NEWS
99 CENTS

Researchers eye more efficient solar cells

By
From page A4 | January 29, 2013 | Leave Comment

Using an exotic form of silicon could substantially improve the efficiency of solar cells, according to computer simulations by researchers at UC Davis and in Hungary.

Solar cells are based on the photoelectric effect: a photon, or particle of light, hits a silicon crystal and generates a negatively charged electron and a positively charged hole. Collecting those electron-hole pairs generates electric current.

Conventional solar cells generate one electron-hole pair per incoming photon, and have a theoretical maximum efficiency of 33 percent. One exciting new route to improved efficiency is to generate more than one electron-hole pair per photon, said Giulia Galli, professor of chemistry at UCD and co-author of the paper, published Jan. 25 in the journal Physical Review Letters.

“This approach is capable of increasing the maximum efficiency to 42 percent, beyond any solar cell available today, which would be a pretty big deal,” said lead author Stefan Wippermann, a postdoctoral researcher at UCD.

“In fact, there is reason to believe that if parabolic mirrors are used to focus the sunlight on such a new-paradigm solar cell, its efficiency could reach as high as 70 percent,” Wippermann said.

Galli said that nanoparticles have a size of nanometers, typically just a few atoms across. Because of their small size, many of their properties are different from bulk materials. In particular, the probability of generating more than one electron-hole pair is much enhanced, driven by an effect called “quantum confinement.”

Experiments to explore this paradigm are being pursued by researchers at the Los Alamos National Laboratory, the National Renewable Energy Laboratory in Golden, Colo., as well as at UCD.

“But with nanoparticles of conventional silicon, the paradigm works only in ultraviolet light,” Wippermann said. “This new approach will become useful only when it is demonstrated to work in visible sunlight.”

The researchers simulated the behavior of a structure of silicon called silicon BC8, which is formed under high pressure but is stable at normal pressures, much as diamond is a form of carbon formed under high pressure but stable at normal pressures.

The computer simulations were run through the National Energy Research Scientific Supercomputing Center at the Lawrence Berkeley Laboratory, which granted the project 10 million hours of supercomputer time.

The simulations demonstrated that nanoparticles of silicon BC8 indeed generate multiple electron-hole pairs per photon even when exposed to visible light.

“This is more than an academic exercise. A Harvard-MIT paper showed that when normal silicon solar cells are irradiated with laser light, the energy the laser emits may create a local pressure high enough to form BC8 nanocrystals. Thus, laser or chemical pressure treatment of existing solar cells may turn them into these higher-efficiency cells,” said co-author Gergely Zimanyi, professor of physics at UCD.

— UC Davis News Service

LEAVE A COMMENT

Discussion | No comments

The Davis Enterprise does not necessarily condone the comments here, nor does it review every post. Read our full policy

.

News

Food insecurity remains an issue for many county residents

By Anne Ternus-Bellamy | From Page: A1

 
4-H members prepare for Spring Show

By Anne Ternus-Bellamy | From Page: A1

 
 
Youth sports in focus on radio program

By Enterprise staff | From Page: A4

 
Rummage sale will benefit preschool

By Enterprise staff | From Page: A4

Concert benefits South Korea exchange

By Enterprise staff | From Page: A4

 
Conference puts focus on Arab studies

By Enterprise staff | From Page: A4

Central Park Gardens to host Volunteer Orientation Day

By Enterprise staff | From Page: A5 | Gallery

 
Volkssporting Club plans North Davis walks

By Enterprise staff | From Page: A5

Hotel/conference center info meeting set

By Enterprise staff | From Page: A5

 
Davis honors ‘green’ citizens

By Enterprise staff | From Page: A5

Water rate assistance bill advances

By Enterprise staff | From Page: A5

 
Program explores STEM careers for girls

By Enterprise staff | From Page: A5

Embroiderers plan a hands-on project

By Enterprise staff | From Page: A5

 
Cycle de Mayo benefits Center for Families

By Anne Ternus-Bellamy | From Page: A8

Author to read ‘The Cat Who Chose to Dream’

By Anne Ternus-Bellamy | From Page: A12

 
.

Forum

Ortiz is the right choice for Yolo

By Letters to the Editor | From Page: A6

 
Tom Meyer cartoon

By Debbie Davis | From Page: A6

The high cost of employment

By Letters to the Editor | From Page: A6

 
High-five to Union Bank

By Letters to the Editor | From Page: A6

Broken sprinklers waste water

By Letters to the Editor | From Page: A6

 
Three more administrators?

By Letters to the Editor | From Page: A6

Neustadt has experience for the job

By Letters to the Editor | From Page: A6

 
Here’s a plan to save big on employee costs

By Special to The Enterprise | From Page: A6

Davis is fair, thoughtful

By Letters to the Editor | From Page: A6

 
.

Sports

DHS/Franklin II is a close loss for Devil softballers

By Enterprise staff | From Page: B1

 
DHS tracksters sweep another DVC meet

By Enterprise staff | From Page: B1 | Gallery

Another DVC blowout for DHS girls soccer

By Evan Ream | From Page: B1 | Gallery

 
Young reinvents his game to help Aggies improve on the diamond

By Bruce Gallaudet | From Page: B1 | Gallery

DHS boys shuffle the deck to beat Cards

By Thomas Oide | From Page: B1 | Gallery

 
Baseball roundup: Giants slam Rockies in the 11th

By The Associated Press | From Page: B2

 
UCD roundup: Aggies lose a softball game at Pacific

By Enterprise staff | From Page: B3

Jahn jumps to Sacramento Republic FC

By Evan Ream | From Page: B8

 
.

Features

.

Arts

Emerson, Da Vinci to present ‘Once Upon a Mattress’

By Enterprise staff | From Page: A11

 
Winters Plein Air Festival begins Friday

By Enterprise staff | From Page: A11

 
Bach Soloists wrap up season on April 28

By Jeff Hudson | From Page: A11

 
Congressional art competition open to high school students

By Enterprise staff | From Page: A11

 
.

Business

.

Obituaries

.

Comics

Comics: Thursday, April 24, 2014

By Creator | From Page: B6