Microgrid Electrode for Si Microwire Solar Cells with a Fill Factor of Over 80%

Abstract

Here, a novel microgrid top electrode for highly efficient radial-junction Si microwire solar cells is demonstrated. The microgrid electrode minimizes optical and electrical losses, thus ensuring proper function of the shallow ( sheet resistance of approximate to 100 Omega sq(-1)) junction emitter. This leads to effective collection of the photocarriers from the shallow junction emitter through the top electrode without severe Auger/ surface recombination, improving the overall power conversion efficiency of the Si microwire solar cell. With an optimized microgrid structure, 1 cm 2 microwire solar cells show a conversion efficiency of up to 16.5%, with an open-circuit voltage of 565.2 mV and a short-circuit current density of 35.9 mA cm - 2; this conversion effi ciencyis 72% higher than that of solar cells with an edge electrode ( 9.6%). Further, an similar to 1 mu m thick Ni electrode that is formed by electroplating considerably reduces the metal and contact resistances, which reproducibly yields a fill factor of over 80% ( max 81.2%). Thus, the use of a novel microgrid to construct an ideal metal/ emitter interface presents a unique opportunity to develop highly efficient microwire solar cells.