Cheaper Yet Efficient Thin Film Solar Cells

Developed jointly by Nanyang Technological University (NTU) and A*STAR Institute of Microelectronics (IME), the new thin-film silicon solar cells are designed to be made from cheaper, low grade silicon. However it is able to generate electricity currents close to that produced by traditional solar cells made from costly, high quality silicon.

The new nano-structured solar cells can produce a current of (34.3mA/cm2) – a world record for a silicon solar cell of its kind. This is made possible by creating a unique texture using nanostructures – which is thousands of times smaller than human hair – on the surface of the solar cell. The resulting electricity current output is close to those of traditional cells (40mA/cm2). Conventional thin film solar cells usually produce about half of the current that traditional cells produce.

Using low-grade amorphous (shapeless) silicon thin film that has no texture – which is over 100 times thinner – addresses the material cost issue, but it is not as effective in converting sunlight to electricity, thus producing less energy. The newly developed nanostructure method, which creates a unique texture on the surface of amorphous silicon, improves the Power Conversion Efficiency (PCE) of the thin film silicon cell and so increases the energy output.

The lead of the project from IME, Doctor Navab Singh, Senior Scientist of IME's NanoElectronics Programme, said: "To mitigate against reduced light absorption and carrier recombination in the amorphous silicon thin film cells, we designed and fabricated the novel nanostructures on silicon surface. The sole application of IME's surface texturing strategy achieved a record high of short circuit current density with 5.26% PCE."

"The cell level power conversion efficiencies of bulk crystalline Si solar cells are 20 – 25%. Given that short circuit current density is directly proportional to PCE, it is conceivable that subsequent efforts to improve fill factor and open circuit voltage would boost the final PCE of the silicon thin film solar cells greatly to match that of bulk Si solar cells. Our future research efforts will explore additional light trapping strategies such as plasmonics," continued Singh.

COMPAMED.de; Source: Nanyang Technological University