Rear-line-contacted silicon concentrator cells on highly and lightly doped substrates

A solar concentrator system with one-axis tracking was developed at ISE Freiburg enabling a high geometrical concentration of around 300×. This system uses a parabolic trough mirror and a three-dimensional second stage consisting of compound parabolic concentrators (CPCs). For this concentrator system and particularly for an easy cell integration we are developing rear-line-contacted concentrator cells (RLCC cells). The RLCC cells have a small active size area of 4.5 mm × 4.5 mm matching with the exit area of the CPCs. In order to optimise the cell efficiency, RLCC cells fabricated on lightly or highly doped substrates are investigated. All cells have a 3 μm high Ti/Pd/Ag metallisation on the rear side. This paper shows that RLCC cells on lightly doped substrates peak at higher concentration than the RLCC cell fabricated on highly doped substrates. Nevertheless, both cell types reach nearly the same maximum efficiency.