A simple and inexpensive fabrication procedure boosts the light-capturing capabilities of tiny holes carved into silicon wafers.
Increasing the cost-effectiveness of photovoltaic devices is critical to making these renewable energy sources competitive with traditional fossil fuels. One possibility is to use hybrid solar cells that combine silicon nanowires with low-cost, photoresponsive polymers.
A straightforward procedure that transforms silver nanospheres (top) into silicon nanoholes (bottom) can overcome the shortcomings of nanowire-based solar cells
Reproduced, with permission, from Ref.1 © 2014 American Institute of Physics
The high surface area and confined nature of nanowires allows them to trap significant amounts of light for solar cell operations. Unfortunately, these thin, needle-like structures are very fragile and tend to stick together when the wires become too long.
Now, findings by Xincai Wang from the A*STAR Singapore Institute of Manufacturing Technology and co-workers from Nanyang Technological University could turn the tables on silicon nanowires by improving the manufacturing of silicon ‘nanoholes’ — narrow cavities carved into silicon wafers that have enhanced mechanical and light-harvesting capabilities(1).
Nanoholes are particularly effective at capturing light because photons can ricochet many times inside these openings until absorption occurs. Yet a practical understanding of how to fabricate these tiny structures is still lacking. One significant problem, notes Wang, is control of the initial stages of nanohole formation — a crucial period that can often induce defects into the solar cell.
Instead of traditional time-consuming lithography, the researchers identified a rapid, ‘maskless’ approach to producing nanoholes using silver nanoparticles. First, they deposited a nanometre-thin layer of silver onto a silicon wafer which they toughened by annealing it using a rapid-burst ultraviolet laser. Careful optimization of this procedure yielded regular arrays of silver nanospheres on top of the silicon surface, with sphere size and distribution controlled by the laser annealing conditions.
Next, the nanosphere–silicon complex was immersed into a solution of hydrogen peroxide and hydrofluoric acid — a mixture that eats away at silicon atoms directly underneath the catalytic silver nanospheres. Subsequent removal of the silver particles with acid produced the final, nanohole-infused silicon surface (see image).
The team analyzed the solar cell activity of their nanohole interfaces by coating them with a semiconducting polymer and metal electrodes. Their experiments revealed a remarkable dependence on nanohole depth: cavities deeper than one micrometer showed sharp drops in power conversion efficiency from a maximum of 8.3 per cent due to light scattering off of rougher surfaces and higher series resistance effects.
“Our simple process for making hybrid silicon nanohole devices can successfully reduce the fabrication costs which impede the solar cell industry,” says Wang. “In addition, this approach can be easily transferred to silicon thin films to develop thin-film silicon–polymer hybrid solar cells with even higher efficiency.”
1. Hong, L., Wang, X., Zheng, H., He, L., Wang, H., Yu, H. & Rusli, E. High efficiency silicon nanohole/organic heterojunction hybrid solar cell. Applied Physics Letters 104, 053104 (2014).
Lee Swee Heng | Research SEA News
Thermo-Optical Measuring method (TOM) could save several million tons of CO2 in coal-fired plants
25.05.2016 | Fraunhofer-Institut für Silicatforschung ISC
Atomic precision: technologies for the next-but-one generation of microchips
24.05.2016 | Fraunhofer-Institut für Lasertechnik ILT
A biological and energy-efficient process, developed and patented by the University of Innsbruck, converts nitrogen compounds in wastewater treatment facilities into harmless atmospheric nitrogen gas. This innovative technology is now being refined and marketed jointly with the United States’ DC Water and Sewer Authority (DC Water). The largest DEMON®-system in a wastewater treatment plant is currently being built in Washington, DC.
The DEMON®-system was developed and patented by the University of Innsbruck 11 years ago. Today this successful technology has been implemented in about 70...
Permanent magnets are very important for technologies of the future like electromobility and renewable energy, and rare earth elements (REE) are necessary for their manufacture. The Fraunhofer Institute for Mechanics of Materials IWM in Freiburg, Germany, has now succeeded in identifying promising approaches and materials for new permanent magnets through use of an in-house simulation process based on high-throughput screening (HTS). The team was able to improve magnetic properties this way and at the same time replaced REE with elements that are less expensive and readily available. The results were published in the online technical journal “Scientific Reports”.
The starting point for IWM researchers Wolfgang Körner, Georg Krugel, and Christian Elsässer was a neodymium-iron-nitrogen compound based on a type of...
In the Beyond EUV project, the Fraunhofer Institutes for Laser Technology ILT in Aachen and for Applied Optics and Precision Engineering IOF in Jena are developing key technologies for the manufacture of a new generation of microchips using EUV radiation at a wavelength of 6.7 nm. The resulting structures are barely thicker than single atoms, and they make it possible to produce extremely integrated circuits for such items as wearables or mind-controlled prosthetic limbs.
In 1965 Gordon Moore formulated the law that came to be named after him, which states that the complexity of integrated circuits doubles every one to two...
Characterization of high-quality material reveals important details relevant to next generation nanoelectronic devices
Quantum mechanics is the field of physics governing the behavior of things on atomic scales, where things work very differently from our everyday world.
When current comes in discrete packages: Viennese scientists unravel the quantum properties of the carbon material graphene
In 2010 the Nobel Prize in physics was awarded for the discovery of the exceptional material graphene, which consists of a single layer of carbon atoms...
24.05.2016 | Event News
20.05.2016 | Event News
19.05.2016 | Event News
27.05.2016 | Awards Funding
27.05.2016 | Life Sciences
27.05.2016 | Life Sciences