Enhancement of photovoltaic characteristics using a PEDOT interlayer in TiO2/MEHPPV heterojunction devices

The effect of inserting a PEDOT interlayer between the MEHPPV layer and the Au electrode of a nanocrystalline ITO/TiO2/MEHPPV/Au heterojunction device on the photovoltaic characteristics of the device has been studied. The MEHPPV layer has both a light-sensitizing role and a hole-transporting function. The overall conversion efficiency of the device with a PEDOT layer is better by more than 80% than that obtainable without a PEDOT layer. The modified device shows improved photocurrent density-voltage (J-V) characteristics, in that there is a strong reduction of the roll-over behavior in the forward bias region, and an increase in the fill factor. These improvements are due to the reduction of junction resistance across the MEHPPV/Au interface in the presence of the PEDOT interlayer, which results in improved hole injection.