TOWARD VERY HIGH EFFICIENCY SILICON CELLS.

A project using a novel silicon solar cell strucure is underway at the University of New South Wales aimed at surpasing the present performance limits of solar cells. The novel MINP solar cell structure is quite similar to the conventional cell structure, having the normal diffused p-n junction, top and rear contacts, and anti-reflection coating. The important difference is that it has a very thin thermal silicon oxide grown along the entire top surface of the silicon substrate. This layer passifies the entire top surface of the cell, giving it near ideal electronic properties. At the same time, the oxide layer is kept very thin, only about 20 angstroms, so that it does not restrict current flow between the top contact and the silicon substrate. With this structure output voltages over 690 millivolts, only marginally short of the target of 700 millivolts, have been obtained. Cells with the energy efficiency in the 16 to 17 percent range have been produced even with the very simple cell design. Efficiencies in the 18 to 19 percent range can be obtained without difficulty.