BURIED CONTACT SILICON SOLAR-CELLS

Despite the growing commercial success of the conventional buried contact solar cell (BCSC), significant improvements in cell performance, simplicity of fabrication, and costs are being made. Five strands to this work with five corresponding variations of the cell structure are responsible for the developments. Hybrid solar cells (standard BCSC front surface with photolithographically defined rear metal contact scheme) have demonstrated open-circuit voltages approaching 700 mV while a simpler cell design requiring no photolithography has demonstrated open-circuit voltages as high as 685 mV. Large area, 20 sun BCSC concentrator cells have been developed with very low metal shading losses (below 3%) due to the redesigning of the groove structure to recess the metal to below the top surface. The resulting record efficiency of 21.5% has been independently confirmed (Sandia). The most recent BCSC structure, where the emphasis is on simplicity and low cost, has the number of high temperature processing steps reduced to one, while efficiencies in the vicinity of those achieved by the conventional BCSC are anticipated. The highest efficiencies demonstrated to date with any of the BCSC structures are well above 21% (Sandia) although all five variations of the BCSC structure appear capable of achieving similar performance levels in the future.