Nanopillars Promise Cheap, Efficient, Flexible Solar Cells
Lawrence Berkeley National Laboratory of the US Department of Energy and University of California at Berkeley have shown a new way to make optically active semiconductors in shape of nanoscale pillars of single crystal size of a billionth meter. Scientist Prof. Ali Javey of Berkeley Lab’s Materials Sciences Division said in spite of holding great promise, manufacture of single-crystalline semiconductors are not economical.
A nano-pillar array’s increased surface area will help collecting more light enhancing its ability to separate electrons from holes thereby producing more electricity. Javey said initial attempts to make photovoltaic cells on nano pillar semiconductors were disappointing and costly as well. Javey’s improved “vapor-liquid-solid” process of dense, highly ordered single-crystal nano-pillars with pillars of electron-rich cadmium sulphide on aluminum foil with geometrically distributed pores derived by anodization which worked as template was grown inside a quart furnace. Nano-pillars were then submerged in a thin layer of hole-rich cadmium telluride collecting the light. The contact between the materials acted as solar cells helping the electrons flow through the nano-pillars to the aluminum contact below, with the holes conducted to thin copper-gold electrodes placed on the surface of the window above.
Although efficiency of this test was at six percent compared to 10 to 18 percent range of mass-produced commercial cells, it was more than most photovoltaic devices based on nanostructured materials, mainly due to the non-transparent copper-gold electrodes which reduced its efficiency by 50 percent. The top-contact transparency is now being improved.
Density and the exposed length of the pillars in contact with the window material decreases the efficiency of a 3-D nanopillar-array solar cell which are being improvised in the future models.
To improve practical applications and theoretical performance, researchers successfully embarked upon a flexible solar cell by reducing the aluminum substrate and replacing the bottom electrode with a thin layer of indium. To make it bendable the cell was covered in clear plastic (polydemethylsiloxane), flexible with marginal effect on performance and without any degradation after repeated bending. Javey believes there are numerous ways to improve 3-D nanopillar photovoltaics for a high performance, simple fabrication process and lower cost of production of solar cells. Growing of single-crystalline structures on large aluminum sheets with 3-D configuration will not only reduce cost but also will do away with stringent quality and purity of the input material. Nanopillar arrays will revolutionize versatile solar modules.
Helios Solar Energy Research Centre, supported by US Department of Energy’s Office of Science, Office of Basic Energy Sciences, is actively supporting this work.
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It only needs the efficiency of PV’s to improve slightly, 1 or 2 %, and then a great deal of money will then be spent, turning the present power network around.
Power Stations (PS) now are only about 30% efficient. Voltage drops the further away, you are from PS.
Instead of remote area’s loosing connection, when there is a storm, they will still have power, whilst urban area’s will not. In UK where I live remote area’s like Scotland and Wales, have some of the network down due to storms at least once a year.
Imagine if you can, 1,000’s of small PV power stations.
So PV’s could be the way to keep the network working.