Electrochemically deposited nano polyaniline films as hole transporting layers in organic solar cells

• This paper compares five surface morphologies of conducting hole-transporting layers.
• The device featuring PANI/PEDOT:PSS as the buffer layer obtains the higher photovoltaic performance.
• The primary doping effect is the main reaction between the interface of PANI and PEDOT:PSS.
• The results of this paper provide a promising means of improving hole transport in organic-based electronics.

In this study, we prepared organic solar cells based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) with electrochemically deposited nano polyaniline (PANI) buffer layers (either PANI – 0.1 M or PANI – 0.3 M) as hole transporting layers and compared their performances with those of solar cells lacking the buffer layer (i.e., bare ITO) or featuring buffer layers of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) or PEDOT:PSS-covered PANI. The power conversion efficiency of the device featuring PANI/PEDOT:PSS as the buffer layer (2.76%) was greater than those of devices featuring bare ITO (0.75%) or the PANI – 0.1 M (1.33%), PANI – 0.3 M (1.78%), or PEDOT:PSS (2.30%) layers. We suspect that the increased conductivity of the PANI/PEDOT:PSS composite, caused by interactions between the PANI nitrogen atoms and the functional groups of PSS, led to additional doping of PANI. This primary doping effect by PSS toward PANI lowered the series resistance of the PANI/PEDOT:PSS buffer layer and, thereby, increased the photocurrent of the device. As a result, electrochemically deposited PANI buffer layers, with or without PEDOT:PSS, appear to be promising hole transporting layers for organic electronic devices that require different candidate materials (other than PEDOT:PSS conductors) and/or different processing conditions (other than spin-coating).

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