Perspectives of applied graphene: Polymer solar cells

Is graphene an interesting material for use in polymer photovoltaic devices? The answer to this question is not clear. Obviously, because indium tin oxide (abbreviated ITO) has become more expensive due to the limited availability of In, graphene has been proposed for use in different types of optoelectric devices, e.g., solar cells (SC), light emitting diodes (LEDs), photosensors (PS), or thin film transistors (FET). However, with respect to organic solar cells, there are currently significantly more theoretical predictions than practical realizations. For this reason, in this review, we would like to discuss the advantages and disadvantages of polymer solar cells that incorporate graphene. Graphene, which is mechanically strong, chemically stable, and inert, should improve the durability and simplify the technology of potential optoelectronic devices. In this review, we discuss the synthetic routes to produce graphene and the photovoltaic properties of organic solar cells based on graphene. With respect to photovoltaic devices, we propose to analyze graphene based on three aspects: (i) as the addition to donor or donor-acceptor materials in the bulk heterojunction (BHJ) organic photovoltaic cells, (ii) as transparent conductive electrodes and (iii) separate layers for organic photovoltaic cells. Photovoltaic (PV) parameters, such as the open circuit voltage (VOC), short circuit current (JSC), fill factor (FF) and power conversion efficiency (η, PCE), are compared for different device architectures.