Potential of PEDOT PSS as a hole selective front contact for silicon heterojunction solar cells

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 vI at the PEDOT PSS c Si interface. An estimated vI of 400 cm 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