  We show that the highly conductive polymer
poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) can
successfully be applied as a hole selective front contact in silicon
heterojunction (SHJ) solar cells. In combination with a superior electron
selective heterojunction back contact based on amorphous silicon (a-Si),
mono-crystalline n-type silicon (c-Si) solar cells reach power conversion
efficiencies up to 14.8% and high open-circuit voltages exceeding 660 mV. Since
in the PEDOT:PSS/c-Si/a-Si solar cell the inferior hybrid junction is
determining the electrical device performance we are capable of assessing the
recombination velocity v_I at the PEDOT:PSS/c-Si interface. An estimated v_I of
~ 400 m/s demonstrates, that while PEDOT:PSS shows an excellent selectivity on
n-type c-Si, the passivation quality provided by the formation of a native
oxide at the c-Si surface restricts the performance of the hybrid junction.
Furthermore, by comparing the measured external quantum efficiency with optical
simulations, we quantify the losses due to parasitic absorption of PEDOT:PSS
and reflection of the device layer stack. By pointing out ways to better
passivate the hybrid interface and to increase the photocurrent we discuss the
full potential of PEDOT:PSS as a front contact in SHJ solar cells.
