Nanowire substrate allows researchers to tune InGaN's response for flexible energy absorption
June 19, 2012 // Julien Happich
To convert as many of the sun's wavelengths as possible, researchers aim at changing the concentration of indium in photovoltaic materials such as indium gallium nitride (InGaN) to tune the material's response so it collects solar energy from a variety of wavelengths.
The more variations designed into the system, the more of the solar spectrum can be absorbed. Though indium gallium nitride, part of a family of materials called III-nitrides, is typically grown on thin films of gallium nitride. Because gallium nitride atomic layers have different crystal lattice spacings from indium gallium nitride atomic layers, the mismatch leads to structural strain that limits both the layer thickness and percentage of indium that can be added. Thus, increasing the percentage of indium added broadens the solar spectrum that can be collected, but reduces the material's ability to tolerate the strain.
Sandia National Laboratories scientists Jonathan Wierer Jr. and George Wang reported in the journal Nanotechnology that if the indium mixture is grown on a phalanx of nanowires rather than on a flat surface, the small surface areas of the nanowires allow the indium shell layer to partially "relax" along each wire, easing strain. This relaxation allowed the team to create a nanowire solar cell with indium percentages of roughly 33 percent, higher than any other reported attempt at creating III-nitride solar cells.
Sandia nanowire template permits flexible energy absorption. Source: Sandia Laboratory
This initial attempt also lowered the absorption base energy from 2.4eV to 2.1 eV, claimed to be the lowest of any III-nitride solar cell to date, and made a wider range of wavelengths available for power conversion. Several unique techniques were used to create the III-nitride nanowire array solar cell. A top-down fabrication process was used to create the nanowire array by masking a gallium nitride (GaN) layer with a colloidal silica mask, followed by dry and wet etching. The resulting array consisted of nanowires with vertical sidewalls and of uniform height.
Next, shell layers containing the higher indium percentage of indium gallium nitride (InGaN) were formed on the GaN nanowire template via metal organic chemical vapor deposition. Lastly, In0.02Ga0.98N was grown, in such a way that caused the nanowires to coalescence. This process produced a canopy layer at the top, facilitating simple planar processing and making the technology manufacturable. The nano-architecture not only enables higher indium proportion in the InGaN layers but also increased absorption via light scattering in the faceted InGaN canopy layer, as well as air voids that guide light within the nanowire array.
Visit Sandia's Laboratory at www.sandia.govAll news
Alps Electric puts cash into Qualtre
December 18, 2014
Alps Electric Co. Ltd. (Tokyo, Japan), a maker of electronics components and infotainment systems, has participated in a ...
China VC lifts sensor startup to record funding
MIT discovers superconductor law
Infrared makes multi-finger gesture control affordable
Smart window tints and acts as transparent battery
Reference design spotlights high-power LED lighting applications
December 17, 2014
Power Integrations has introduced a reference design for LED streetlights, high-bay lights and other high-power LED-lighting ...
Tiny spectrometer targets IoT
Feeding scrap plastic into your designs
LG adds quantum dot technology to 4K ULTRA HD TVs
- New life for Embedded systems in the Internet of Things
- Virtualization and the Internet of Things
- RF/Microwave Instrumentation “S” Series Amplifiers
- Application Guide to RF Coaxial Connectors and Cables
InterviewCEO interview: Bosch's IoT startup is all about the system
Thorsten Mueller, CEO of Bosch Connected Devices and Solutions GmbH (Reutlingen, Germany), has been guiding the latest startup subsidiary of Robert Bosch GmbH since 2013 when he started the initiative ...
Filter WizardCheck out the Filter Wizard Series of articles by Filter Guru Kendall Castor-Perry which provide invaluable practical Analog Design guidelines.
Linear video channel
READER OFFERRead more
This month, Arrow Electronics is giving away ten BeMicro Max 10 FPGA evaluation boards together with an integrated USB-Blaster, each package being worth 90 Euros, for EETimes Europe's readers to win.
Designed to get you started with using an FPGA, the BeMicro Max 10 adopts Altera's non-volatile MAX 10 FPGA built on 55-nm flash process.
The MAX 10 FPGAs are claimed to revolutionize...MORE INFO AND LAST MONTH' WINNERS...
December 15, 2011 | Texas instruments | 222901974
Unique Ser/Des technology supports encrypted video and audio content with full duplex bi-directional control channel over a single wire interface.