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
New welding process joins dissimilar sheets better
28.09.2016 | Technologie Lizenz-Büro (TLB) der Baden-Württembergischen Hochschulen GmbH
Cooling buildings with solar heat
26.09.2016 | FIZ Karlsruhe – Leibniz-Institut für Informationsinfrastruktur GmbH
Friction stir welding is a still-young and thus often unfamiliar pressure welding process for joining flat components and semi-finished components made of light metals.
Scientists at the University of Stuttgart have now developed two new process variants that will considerably expand the areas of application for friction stir welding.
Technologie-Lizenz-Büro (TLB) GmbH supports the University of Stuttgart in patenting and marketing its innovations.
Friction stir welding is a still-young and thus often unfamiliar pressure welding process for joining flat components and semi-finished components made of...
Optical quantum computers can revolutionize computer technology. A team of researchers led by scientists from Münster University and KIT now succeeded in putting a quantum optical experimental set-up onto a chip. In doing so, they have met one of the requirements for making it possible to use photonic circuits for optical quantum computers.
Optical quantum computers are what people are pinning their hopes on for tomorrow’s computer technology – whether for tap-proof data encryption, ultrafast...
The Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP has been developing various applications for OLED microdisplays based on organic semiconductors. By integrating the capabilities of an image sensor directly into the microdisplay, eye movements can be recorded by the smart glasses and utilized for guidance and control functions, as one example. The new design will be debuted at Augmented World Expo Europe (AWE) in Berlin at Booth B25, October 18th – 19th.
“Augmented-reality” and “wearables” have become terms we encounter almost daily. Both can make daily life a little simpler and provide valuable assistance for...
With the help of artificial intelligence, chemists from the University of Basel in Switzerland have computed the characteristics of about two million crystals made up of four chemical elements. The researchers were able to identify 90 previously unknown thermodynamically stable crystals that can be regarded as new materials. They report on their findings in the scientific journal Physical Review Letters.
Elpasolite is a glassy, transparent, shiny and soft mineral with a cubic crystal structure. First discovered in El Paso County (Colorado, USA), it can also be...
For the first time, Fraunhofer IKTS shows additively manufactured hardmetal tools at WorldPM 2016 in Hamburg. Mechanical, chemical as well as a high heat resistance and extreme hardness are required from tools that are used in mechanical and automotive engineering or in plastics and building materials industry. Researchers at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS in Dresden managed the production of complex hardmetal tools via 3D printing in a quality that are in no way inferior to conventionally produced high-performance tools.
Fraunhofer IKTS counts decades of proven expertise in the development of hardmetals. To date, reliable cutting, drilling, pressing and stamping tools made of...
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