Organic Photovoltaics with Stacked Graphene Anodes

Graphene has recently been used to achieve power conversion efficiencies (PCEs) equal to those of ITO-based devices, although they remain a challenging and costly replacement for ITO. Herein, we employed chemical vapor deposition to grow graphene islands and transferred them onto a transparent substrate. The resulting stacked graphene films were characterized by Raman and UV–vis spectroscopies and conductivity measurements. Solar cells fabricated with stacked graphene (one to four layers)/PEDOT:PSS/P3HT:PCBM/Ca/Al architecture showed an enhancement of PCE as a function of the number of stacked layers. The highest efficiency was measured for the double-layered graphene anode because of its optimal conductance and transmittance. This work establishes that readily prepared layered graphene islands are a viable and economical substitute for ITO.