A Graphene-Carbon Nanotube Hybrid Material for Photovoltaic Applications

TL;DR

This paper presents a graphene-CCNT hybrid material with significantly reduced sheet resistance and maintained transparency, suitable for photovoltaic transparent electrodes, achieved through fabrication, doping, and modeling.

Contribution

The study introduces a novel graphene-CCNT hybrid with enhanced electrical properties and stability, supported by a 2D resistance network model.

Findings

Sheet resistance halved by hybridization

Chemical doping further reduces resistance

Hybrid exhibits improved stability over doped graphene

Abstract

Large area graphene sheets grown by chemical vapor deposition can potentially be employed as a transparent electrode in photovoltaics if their sheet resistance can be significantly lowered, without any loss in transparency. Here, we report the fabrication of a graphene-conducting-carbon-nanotube (CCNT) hybrid material with a sheet resistance considerably lower than neat graphene, and with the requisite small reduction in transparency. Graphene is deposited on top of a a self-assembled CCNT monolayer which creates parallel conducting paths on the graphene surface. The hybrid thereby circumvents electron scattering due to defects in the graphene sheet, and reduces the sheet resistance by a factor of two. The resistance can be further reduced by chemically doping the hybrid. Moreover, the chemically doped hybrid is more stable than a standalone chemically doped graphene sheet, as the CCNT network enhances the dopant binding. In order to understand the results, we develop a 2D resistance network model in which we couple the CCNT layer to the graphene sheet and demonstrate the model accounts quantitatively for the resistance decrease. Our results show that a graphene-CCNT hybrid system has high potential for use as a transparent electrode with high transparency and low sheet resistance.