Light intensity dependent characteristics of micro-textured Si/PEDOT:PSS heterojunction solar cell

Heterojunction solar cells made of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and Si have attracted a lot of attention towards low-cost and efficient devices. Here, heterojunction solar cell using pristine PEDOT:PSS on micro-textured n-Si has been fabricated. Effect of light intensity on photovoltaic characteristics of PEDOT:PSS/Si cells has been investigated via current (J) versus voltage (V) characteristics and quantum efficiency (EQE) measurements. It is found that photocurrent (J(sc)) of such cells deteriorates drastically at higher light intensities resulting in quite low J(sc) ( 15.0 mA/cm(2)) in J-V response under intense white light than that obtained from EQE measurements (> 30.0 mA/cm(2)) under low intensity monochromatic light. The observed effect of light intensity on the cell performances is reversible. Structural stability of PEDOT:PSS layer is also investigated by Raman spectroscopy. No post high intensity light exposure structural transformation in the PEDOT:PSS layer is observed. The observed light sensitive photoresponse of such cells has been attributed to possible light induced instantaneous structural changes in the PEDOT:PSS layer leading to reduced charge carrier dynamics and hence the formation of space charge region at PEDOT:PSS/Si interface at higher intensities. Further, the EQE with varying intensity is done which can help to optimize the illumination condition for such cell. The present study opens up new area of intensive research required in order to optimize polymer layer properties and improving the performance of PEDOT:PSS/Si solar cell leading to efficient, stable and low cost heterojunction solar cell technology.