Improved performance of organic photovoltaic devices by doping F4TCNQ onto solution-processed graphene as a hole transport layer

Interfacial engineering is crucial for the stability and efficiency of organic solar cells. PEDOT:PSS, which has been widely used as a hole transport layer, has stability issues when exposed to air because of its acidic and hygroscopic nature. Herein, we investigated the electrical properties of reduced graphene oxide covered with an F(4)TCNQ interfacial layer as an alternative and its effect on the photovoltaic performance. Using an array of charge transport, spectroscopic and imaging techniques we found that the reduced graphene oxide film is efficiently hole-doped through an interfacial charge transfer, which enhances its electrical properties and favorably modifies its work function. Consequently, the open-circuit voltage and fill factor of solar cells incorporating such films are improved. P3HT might also be hole-doped by F(4)TCNQ, due to the formation of an intermixed interfacial layer, resulting in an increase of power conversion efficiency. (C) 2016 Elsevier B.V. All rights reserved.