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
Multithreading boosts ThreadX on MIPS cores
December 06, 2013
Imagination Technologies and Express Logic have expanded their support of the ThreadX real time operating system on Imagination’s ...
UK distribution sees 5% growth in 2014
Global M2M innovations design contest
PHI Group plans acquisition Nord Energy to extend LED street lighting offering
EV market is much more than passenger cars - and it's booming
Stanene may be better than Graphene
December 06, 2013
A team of researchers led by Stanford University professor Shoucheng Zhang now have high hopes that a new material they call ...
US demand for LED lighting to grow more than 10 percent annually to 2017, reports Freedonia
Women demand different connectivity functions in the car
Advanced batteries reached $10.8bn in market value in 2012, reports Navigant Research
- 3mm × 3mm QFN IC Directly Monitors 0V to 80V Supplies
- UltraCMOS® Semiconductor Technology Platforms: A Rapid Advancement of Process & Manufacturing
- Adaptive Cell Converter Topology Enables Constant Efficiency in PFC Applications
- Isolated 4-Channel, Thermocouple/RTD Temperature Measurement System with 0.5°C Accuracy
InterviewPerformance monitoring solution helps provide intelligent control of high power systems
A performance monitoring solution designed to enable companies to monitor high power IGBT module systems in locomotive, wind turbine, High Voltage DC and industrial drive applications was unveiled this ...
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
Internet of Things (IoT) manufacturer Ciseco has launched the Raspberry Pi ‘Wireless Inventors Kit’ (RasWIK), featuring 88 pieces to provide everything a Pi owner needs to follow a series of step-by-step projects or to create their own wireless devices, without the need for configuration or even writing code.
RasWIK has been designed to be highly accessible, demystifying the dark art of wireless and enabling anyone with basic computing skills to begin building wireless devices with a Raspberry Pi. You can create anything from a simple traffic light, to a battery monitor, or even a temperature gauge that sends data to the Xively IoT cloud so billions can access the data.This month, Ciseco is giving away twelve Raspberry Pi Wireless Inventors kits, worth £49.99 each for EETimes Europe's readers to win.
And the winners are...
In our previous reader offer, Farsens was giving away five kits for EEtimes Europe readers to evaluate its FenixVortex, Kineo and X1 wireless, battery free sensor tags.
Lucky winners include Mr A. Neil from the UK, Mr. E. Delvaux from Belgium, Mr Lengal from the Czech Republic, Mr H. Bijlsma from the Netherlands, and Mr G. Pfaff from Germany. All should be receiving their packages soon. Lets wish them some interesting findings with their projects.
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.