Utilization of conducting polymers in rectifying junction construction: Dark characteristics and photovoltaic properties

The electrical characteristics of the junction obtained by depositing poly(4,4′-dipentoxy-2,2′-bithiophene) onn-type silicon have been investigated in the dark and under white as well as monochromatic illumination. The dark forward current is space charge limited at forward bias >0·2 V, whereas it has an exponential trend for very low forward voltages. A Schottky barrier formation at the poly(ET2)/n-Si interface is demonstrated. The barrier height values, obtained both from the Mott-Schottky plot and from the dependence of the open-circuit voltage on the short-circuit current, are very similar. The short-circuit current is a linear function of the incident light intensity, as expected for silicon solar cells. The analysis of the spectral response of the junction suggests that the photocurrent is mainly due to silicon.