Au-doped single layer graphene nanoribbons for a record-high efficiency ITO-free tandem polymer solar cell
Polymer solar cells (PSCs) are apparently becoming one of the leading technologies to reduce our dependency on traditional power sources. However, the frequent use of a transparent conductive electrode, indium-tin-oxide (ITO), in the present PSC technologies has increased the overall expenses. In addition, its brittleness in nature could limit the future development of PSCs, particularly in a flexible format. Here, we report on the development of Au-doped single layer graphene nanoribbons (Au-doped SLGNRs) as an option to the transparent conducting electrode (indium tin oxide, ITO) that could yield a single-layer PSC with power conversion and external quantum efficiencies comparable to commonly used transparent electrodes. When the Au-doped SLGNRs are implemented in tandem architecture, a power conversion efficiency (PCE) of 8.48% is achieved. This is the highest efficiency for ITO-free tandem PSCs to date. The improved performance of the Au-doped SLGNR anode is characterized to the structure of the device that enables a hole transport from the active layer into the Au-doped SLGNR anode.