Light intensity and spectral dependence characteristics of silicon nanowire/PEDOT:PSS heterojunctions solar cells

Recently, research on Si/conducting organic polymer heterojunction solar cells has gained prominence owing to their low fabrication cost and potential for reasonably good efficiency. Poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) coated over n-type Si forms such heterojunction which has theoretical capabilities comparable to the conventional p-n Si junction. However these devices still need fabrication parameters optimization in order to compete with conventional p-n junction silicon solar cells. Here, we report the photoresponse of Ag/PEDOT:PSS/n-SiNW/Al solar cell at different light intensities and different wavelengths. The device is fabricated by spin coating the PEDOT:PSS over n-Si NW based Si substrates. It is further noted that the short circuit current is significantly lower in J-V response than that derived from external quantum efficiency measurements. It is observed that the photocurrent density and fill factor deteriorates significantly at higher intensities. This is suggestive of some space charge build up at Si-PEDOT:PSS interface at higher intensities because of difference in hole mobility in Si and PEDOT:PSS. This could also be strongly attributed to structural changes in the PEDOT:PSS layer which might change the charge carrier dynamics and hence the electrical response of the layer. The response of cell with varying intensity can help to optimize the illumination condition for the cell. The wavelength response of the cell can help us better understand the solar cell working and can help in optimizing the fabrication parameters. This opens up new area of intensive research required in order to optimize polymer layer properties and improving the performance of PEDOT:PSS/SiNW-based solar cell.