Screen-Printed Al-Alloyed Rear Junction Solar Cell Concept Applied to Very Thin (100 μm) Large-Area n-Type Si Wafers

Abstract

Reducing the thickness of crystalline Si wafers processed to solar cells returns two significant benefits. Firstly, processing cost is reduced by saving cost- and energy-intensive Si material. Secondly, the required diffusion length of minority carriers is smaller, thus, wafers with a smaller carrier lifetime (e.g. due to higher base doping) can be utilized. In this work, the industrially feasible “PhosTop” cell concept is employed by manufacturing large-area n-type rear junction solar cells with a screen-printed Al-alloyed emitter featuring a selective phosphorous front surface field and a SiO2/SiNx passivation on the front.PC1D simulations for substrates with different base doping concentrations show that the range of base resistivities utilizable for those PhosTop solar cells is extended towards higher doping concentrations with decreasing wafer thickness. PC1D forecasts a conversion efficiency of the chosen 2.8Ωcm n-type Czochralski-Si wafers of 19.2% for 100μm thickness, merely 0.1% less than for standard thickness but saving ∼25% of the Si material. The manufactured thin large-area solar cells achieve a maximum efficiency of 19.0%.