Large‐Area PEDOT:PSS/c‐Si Heterojunction Solar Cells With Screen‐Printed Metal Contacts

A large‐area BackPEDOT solar cell with a phosphorus‐diffused emitter and a high‐temperature‐fired screen‐printed Ag grid on the front surface and PEDOT:PSS as hole‐collecting and passivating layer at the cell rear is developed. As base material, 15.6 × 15.6 cm 2 pseudo‐square industrial‐type boron‐doped p ‐type Czochralski‐grown silicon wafers are used. The set‐peak firing temperature ( T set ) is varied from 850 to 870 °C with a total number of 32 processed solar cells. The optimum T set of 870 °C results in a median solar cell efficiency of 19.0%. The best large‐area BackPEDOT solar cell achieves an efficiency of 20.2%. Based on external quantum efficiency measurements, a rear surface recombination velocity S rear  < 70 cm s −1 is determined, a value which is on a par with today's industrial high‐efficiency solar cells. Furthermore, a low‐temperature metal paste is introduced, which is shown to be capable of metalizing the PEDOT:PSS‐covered rear surface of the solar cells without damaging the rear surface passivation. The principle feasibility of such a rear metallization scheme is demonstrated. The parasitic absorption of infrared light within the PEDOT:PSS layer is identified as the major loss mechanism in the current cells, which might be overcome in the future by adding infrared‐transparent additives to the PEDOT:PSS dispersion.