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
Iron fluoride to triple energy storage?
April 21, 2015
Researchers the University of Wisconsin–Madison and Brookhaven National Laboratory have developed a novel X-ray imaging technique ...
EMEA PC shipments resume steady decline
Nohau to resell Icon Labs' security portfolio in Scandinavia
Distribution deal for Silex Technology wireless connectivity, with Arrow
MIT accessorizes your thumbnail with track pad
MINI giving drivers a peek at 'augmented reality'
April 20, 2015
Although most drivers have yet to embrace the idea of head-up displays (HUDs) on windshields, MINI is leapfrogging to the ...
Moore's Law: a mixed-signal perspective
Connected LED opens path to 'intelligent cities'
Magnesium ions for car batteries
- Smart Capacitive Design Tips
- Wireless MCUs and IoT
- Battery Management System Tutorial
- Deciding if Automated Test is right for your Company
InterviewInfineon: CAN FD success goes at the expense of FlexRay
The faster version of the venerable CAN bus, CAN FD is currently taking off at several carmakers. Infineon's Thomas Böhm, Head of Body / Automotive, believes this could well go at the expense of FlexRay. ...
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, DecaWave is offering EETimes Europe's readers the chance to win two TREK1000 kits to evaluate its Ultra-Wideband (UWB) indoor location and communication DW1000 chip in different real-time location system topologies.
Worth €947, the kit allow designers to prove a concept within hours and have a prototype ready in days. Based on the two-way ranging scheme, the kit lets you test...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.